02-24-2017, 10:05 AM

PHY101 Physics short questions and answers collection for preparation of Exams.

Question:

What is the difference between kinetic and static friction?

Answer:

1.Static friction: The friction that exists between two surfaces that are not moving relative to each other. 2.Kinetic friction: The friction that exists between two surfaces that are moving relative to each other.

Question:

What is flux in Physics?

Answer:

The word flux has many meanings, but in physics flux is the "rate of flow" of some quantity through an area. The thing "flowing" could be a fluid (like air or water), some form of energy (like heat, light, or radio waves), or a field (gravitational, electric, or magnetic). In the case of fields, however, the idea of "flow" is more poetic than literal.

Question:

What is impulse?

Answer:

The simple definition for impulse is that it is a change in momentum. If you apply a force on an object 1 s then you see small change in the momentum. However, if you apply force on an object long period of time then you see the amount of change in momentum is bigger than the first situation. In summary, I try to say that impulse is the multiplication of applied force and time interval it applied. Impulse is also a vector quantity having both magnitude and direction. It has the same direction with applied net force. Impulse = Force*Time Interval

Question:

A potter’s wheel rotates. A location farther from the axis will have a greater angular velocity than one closer to the axis. Either yes or no explain in each case.

Answer:

Wrong. They all have the same angular displacement over time, which means they have the same angular velocity, as well. In contrast, they do have different linear (tangential) velocities.

Question:

Wave speed in a string is a function of frequency, so if I increase the wave frequency, will the wave speed increase too?

Answer:

No. The speed of a wave in a string is fixed by the tension and linear density of the string. Increasing wave frequency will cause a decrease in wavelength, but no change in wave speed.

Question:

If the gravitational force on an object is directly proportional to its mass, why don't objects with large masses fall with greater acceleration than small ones?

Answer:

Because g is the same for all objects near the Earth's surface. The larger mass needs a larger force to give it just the same acceleration

Question:

How can we convert radian to degree measure and vice versa?

Answer:

First you should clear about, what is the relationship between degrees and radians? It's easy to figure out. We know that a straight angle is 180 degrees and it has a measure of p radians. Therefore 180° = p radians. Hence we get 1 rad = (180/ p)°, and 1° = (p /180) rad. Let's look at some examples. Find the radian measure of 60° Solution: Now since we want to convert degrees to radians, we have to multiply by p /180. Therefore, we get: 60° = 60(p /180) rad = p/3 rad Example 2: Find the radian measure of 225° Solution: Again we have to multiply by p/180 since we are changing degrees to radians. 225° = 225(p/180) = 5p/4 rad

Question:

What is concept of black hole?

Answer:

The concept about black hole is as under, “If enough mass is concentrated in a small enough region of space-time, the space-time curvature can become infinite. The pull of gravity in this case becomes so strong that nothing, not even light, can escape this region. Such objects are called black holes and the boundary which marks the region out of which nothing can escape anymore is called an event horizon”.

Question:

What is inertia?

Answer:

Inertia “Objects tend to "keep on doing what they're doing." In fact, it is the natural tendency of objects to resist changes in their state of motion. This tendency to resist changes in their state of motion is described as inertia.

Question:

Can we consider mass as a weight and weight as a mass?

Answer:

Note that weight and mass are two different quantities. To understand the differences we need to compare a few points: 1) Mass is a measurement of the amount of matter something contains, while Weight is the measurement of the pull of gravity on an object. 2) Mass is measured by using a balance comparing a known amount of matter to an unknown amount of matter. Weight is measured on a scale. 3) The Mass of an object doesn't change when an object's location changes. Weight, on the other hand does change with location.

Question:

What are the applications of trigonometry in Daily life?

Answer:

Here are some applications of trigonometry in real life. 1)It is used in navigation to find the distance of the shore from a point in the sea. 2)Trigonometry is commonly used in finding the height of towers and mountains. 3)Architects use trigonometry to calculate structural load, roof slopes, ground surfaces and many other aspects, including sun shading and light angles. 4)The sine and cosine functions are fundamental to the theory of periodic functions such as those that describe sound and light waves. 5)It is used in finding the distance between celestial bodies. 6)It is used in oceanography in calculating the height of tides in oceans.

Question:

I. What is Fourier analysis? II. What is principal of superposition?

Answer:

I.The mathematician Fourier proved that any continuous function could be produced as an infinite sum of sine and cosine waves II.A principle holding that two or more solutions to a linear equation or set of linear equations can be added together so that their sum is also a solution.

Question:

Does the escape speed of a rocket depend on its mass? Explain

Answer:

No, the escape speed does not depend on the mass of the rocket. If a rocket is launched at escape speed, then the total energy of the rocket-Earth system will be zero. When the separation distance becomes infinite (U = 0) the rocket will stop (K = 0).

Question:

If Earth were to spin faster about its axis, your weight would be less. If you were in a rotating space habitat that increased its spin rate, you'd "weigh" more. Explain why greater spin rates produce opposite effects in these cases.

Answer:

You're on the outside of the spinning Earth, but you'd be on the inside of a spinning space habitat. A greater spin rate on the outside of the Earth tends to throw you off a weighing scale, causing it to show a decrease in weight, but against a weighing scale inside the space habitat to show an increase in weight.

Question:

Does a tuning fork or similar tuning instrument undergo SHM? Why is this crucial question for a musician?

Answer:

Yes the oscillations of a tanning fork are essentially simple harmonic motion, which means they will always vibrate at the same frequency, independent of amplitude. This is why a tuning fork can be used as a standard for a musical pitch.

Question:

Explain why no work is done on a planet as it moves in a circular orbit around the Sun, even though a gravitational force is acting on the planet. What is the net work done on a planet during each revolution as it moves around the Sun in an elliptical orbit?

Answer:

In a circular orbit each increment of displacement is perpendicular to the force applied. The dot product of force and displacement is zero. The work done by the gravitational force on a planet in an elliptical orbit speeds up the planet at closest approach, but negative work is done by gravity and the planet slows as it sweeps out to its farthest distance from the Sun. Therefore, net work in one complete orbit is zero.

Question:

Explain why a sealed bottle partially filled with a liquid can float in a basin of the same liquid

Answer:

The glass may have higher density than the liquid, but the air inside has lower density. The total weight of the bottle can be less than the weight of an equal volume of the liquid.

Question:

Suppose you are standing directly behind someone who steps back and accidentally stomps on your foot with the heel of one shoe. Would you be better off if that person were (a) a large professional basketball player wearing sneakers (b) a petite woman wearing spike-heeled shoes?

Answer:

I would be better off if that person were a large professional basketball player wearing sneakers, because of less pressure exerted. Since pressure is equal to force per unit area. Area in part (b) is less than part (a). So, the pressure exerted in part (a) will be less than that of in part (b). Answer: (a). Because the basketball player’s weight is distributed over the larger surface area of the shoe, the pressure (F / A) that he applies is relatively small. The woman’s lesser weight is distributed over the very small cross-sectional area of the spiked heel, so the pressure is high.

Question:

The centre of mass of a championship-level high jumper passes below the bar even though the jumper passes above the bar. How is this possible?

Answer:

The body is curved like a horseshoe “drapped” over the bar. So only part of the body is above the bar.

Question:

A light, uncharged metallic sphere suspended from a thread is attracted to a charged rubber rod. After it touches the rod, the sphere is repelled by the rod. Explain.

Answer:

The electric field due to the charged rod induces charges on near and far sides of the sphere. The attractive Coulomb force of the rod on the dissimilar charge on the close side of the sphere is larger than the repulsive Coulomb force of the rod on the like charge on the far side of the sphere. The result is a net attraction of the sphere to the rod. When the sphere touches the rod, charge is conducted between the rod and the sphere, leaving both the rod and the sphere like-charged. This results in a repulsive Coulomb force.

Question:

Charge is said to be quantized. What does it mean? Explain.

Answer:

Charge is quantized. This means that charge come certain units only. So the size of a charge can only be, 0, ±e, ±2e, ±3e …where e = 1.602 * 10-19 C is the value of the charge present on a proton.

Question:

What is Fourier analysis?

Answer:

The mathematician Fourier proved that any continuous function could be produced as an infinite sum of sine and cosine waves

Question:

A 20 dB sound is twice as intense as a 10 dB sound, explain it.

Answer:

No, the decibel measurement system is logarithmic. The 20 dB sound has ten times the intensity: ten times as many watts per square meter. A typical person perceives it as twice as loud.

Question:

Many traffic lights change when a car rolls up to the intersection. How does the light sense the presence of the car?

Answer:

Traffic light sensors work by measuring the change in inductance of a coil embedded under the road surface when a car drives over it.

Question:

Which is denser, dry air or air saturated with water vapor? Explain.

Answer:

The dry air is denser. Since the air and the water vapor are at the same temperature, they have the same kinetic energy per molecule. For a controlled experiment, the humid and dry air is at the same pressure, so the number of molecules per unit volume must be the same for both. The water molecule has a smaller molecular mass (18.0 u) than any of the gases that make up the air, so the humid air must have the smaller mass per unit volume.

Question:

Is it true that de Broglie wavelength associated with particles like protons and electrons only? Or it is applicable to larger things like baseballs also, explain it.

Answer:

No. The wavelengths of objects with relatively large momenta, such as moving baseballs, are so small that experiments do not reveal their wave-like properties. But these objects are still subject to the laws of quantum physics. For large objects moving at ordinary speeds, the predictions of quantum physics and those of Newtonian mechanics are identical for all intents and purposes, much as special relativity essentially agrees with Newtonian mechanics at slow enough speeds.

Question:

Is a black body black? Explain by giving solid reason.

Answer:

No. The "blackness" of a black body refers to its ideal property of absorbing all radiations incident on it. If a room-temperature object absorbs all radiation, we describe it as (visibly) black. The black appearance, however, is due to the fact that our eyes are sensitive only to visible light. If we could detect radiation with our eyes, we would see the object emitting radiation. If the temperature of the black body is raised, Wien's Law and Stefan's Las tell us that sufficient radiation will be emitted in the visible range for the object to glow visibly. Thus the black body could appear possibly as red, while, or blue, depending on its temperature

Question:

Two solid blocks of identical size are submerged in water. One block is lead and the other is aluminum. Upon which is the buoyant force greater?

Answer:

The buoyant force is the same on each, for both blocks displace the same volume of water. For submerged objects, only the volume of water displaced, not the object's weight, determines the buoyant force.

Question:

What is the difference between kinetic and static friction?

Answer:

1.Static friction: The friction that exists between two surfaces that are not moving relative to each other. 2.Kinetic friction: The friction that exists between two surfaces that are moving relative to each other.

Question:

What is flux in Physics?

Answer:

The word flux has many meanings, but in physics flux is the "rate of flow" of some quantity through an area. The thing "flowing" could be a fluid (like air or water), some form of energy (like heat, light, or radio waves), or a field (gravitational, electric, or magnetic). In the case of fields, however, the idea of "flow" is more poetic than literal.

Question:

What is impulse?

Answer:

The simple definition for impulse is that it is a change in momentum. If you apply a force on an object 1 s then you see small change in the momentum. However, if you apply force on an object long period of time then you see the amount of change in momentum is bigger than the first situation. In summary, I try to say that impulse is the multiplication of applied force and time interval it applied. Impulse is also a vector quantity having both magnitude and direction. It has the same direction with applied net force. Impulse = Force*Time Interval

Question:

A potter’s wheel rotates. A location farther from the axis will have a greater angular velocity than one closer to the axis. Either yes or no explain in each case.

Answer:

Wrong. They all have the same angular displacement over time, which means they have the same angular velocity, as well. In contrast, they do have different linear (tangential) velocities.

Question:

Wave speed in a string is a function of frequency, so if I increase the wave frequency, will the wave speed increase too?

Answer:

No. The speed of a wave in a string is fixed by the tension and linear density of the string. Increasing wave frequency will cause a decrease in wavelength, but no change in wave speed.

Question:

If the gravitational force on an object is directly proportional to its mass, why don't objects with large masses fall with greater acceleration than small ones?

Answer:

Because g is the same for all objects near the Earth's surface. The larger mass needs a larger force to give it just the same acceleration

Question:

How can we convert radian to degree measure and vice versa?

Answer:

First you should clear about, what is the relationship between degrees and radians? It's easy to figure out. We know that a straight angle is 180 degrees and it has a measure of p radians. Therefore 180° = p radians. Hence we get 1 rad = (180/ p)°, and 1° = (p /180) rad. Let's look at some examples. Find the radian measure of 60° Solution: Now since we want to convert degrees to radians, we have to multiply by p /180. Therefore, we get: 60° = 60(p /180) rad = p/3 rad Example 2: Find the radian measure of 225° Solution: Again we have to multiply by p/180 since we are changing degrees to radians. 225° = 225(p/180) = 5p/4 rad

Question:

What is concept of black hole?

Answer:

The concept about black hole is as under, “If enough mass is concentrated in a small enough region of space-time, the space-time curvature can become infinite. The pull of gravity in this case becomes so strong that nothing, not even light, can escape this region. Such objects are called black holes and the boundary which marks the region out of which nothing can escape anymore is called an event horizon”.

Question:

What is inertia?

Answer:

Inertia “Objects tend to "keep on doing what they're doing." In fact, it is the natural tendency of objects to resist changes in their state of motion. This tendency to resist changes in their state of motion is described as inertia.

Question:

Can we consider mass as a weight and weight as a mass?

Answer:

Note that weight and mass are two different quantities. To understand the differences we need to compare a few points: 1) Mass is a measurement of the amount of matter something contains, while Weight is the measurement of the pull of gravity on an object. 2) Mass is measured by using a balance comparing a known amount of matter to an unknown amount of matter. Weight is measured on a scale. 3) The Mass of an object doesn't change when an object's location changes. Weight, on the other hand does change with location.

Question:

What are the applications of trigonometry in Daily life?

Answer:

Here are some applications of trigonometry in real life. 1)It is used in navigation to find the distance of the shore from a point in the sea. 2)Trigonometry is commonly used in finding the height of towers and mountains. 3)Architects use trigonometry to calculate structural load, roof slopes, ground surfaces and many other aspects, including sun shading and light angles. 4)The sine and cosine functions are fundamental to the theory of periodic functions such as those that describe sound and light waves. 5)It is used in finding the distance between celestial bodies. 6)It is used in oceanography in calculating the height of tides in oceans.

Question:

I. What is Fourier analysis? II. What is principal of superposition?

Answer:

I.The mathematician Fourier proved that any continuous function could be produced as an infinite sum of sine and cosine waves II.A principle holding that two or more solutions to a linear equation or set of linear equations can be added together so that their sum is also a solution.

Question:

Does the escape speed of a rocket depend on its mass? Explain

Answer:

No, the escape speed does not depend on the mass of the rocket. If a rocket is launched at escape speed, then the total energy of the rocket-Earth system will be zero. When the separation distance becomes infinite (U = 0) the rocket will stop (K = 0).

Question:

If Earth were to spin faster about its axis, your weight would be less. If you were in a rotating space habitat that increased its spin rate, you'd "weigh" more. Explain why greater spin rates produce opposite effects in these cases.

Answer:

You're on the outside of the spinning Earth, but you'd be on the inside of a spinning space habitat. A greater spin rate on the outside of the Earth tends to throw you off a weighing scale, causing it to show a decrease in weight, but against a weighing scale inside the space habitat to show an increase in weight.

Question:

Does a tuning fork or similar tuning instrument undergo SHM? Why is this crucial question for a musician?

Answer:

Yes the oscillations of a tanning fork are essentially simple harmonic motion, which means they will always vibrate at the same frequency, independent of amplitude. This is why a tuning fork can be used as a standard for a musical pitch.

Question:

Explain why no work is done on a planet as it moves in a circular orbit around the Sun, even though a gravitational force is acting on the planet. What is the net work done on a planet during each revolution as it moves around the Sun in an elliptical orbit?

Answer:

In a circular orbit each increment of displacement is perpendicular to the force applied. The dot product of force and displacement is zero. The work done by the gravitational force on a planet in an elliptical orbit speeds up the planet at closest approach, but negative work is done by gravity and the planet slows as it sweeps out to its farthest distance from the Sun. Therefore, net work in one complete orbit is zero.

Question:

Explain why a sealed bottle partially filled with a liquid can float in a basin of the same liquid

Answer:

The glass may have higher density than the liquid, but the air inside has lower density. The total weight of the bottle can be less than the weight of an equal volume of the liquid.

Question:

Suppose you are standing directly behind someone who steps back and accidentally stomps on your foot with the heel of one shoe. Would you be better off if that person were (a) a large professional basketball player wearing sneakers (b) a petite woman wearing spike-heeled shoes?

Answer:

I would be better off if that person were a large professional basketball player wearing sneakers, because of less pressure exerted. Since pressure is equal to force per unit area. Area in part (b) is less than part (a). So, the pressure exerted in part (a) will be less than that of in part (b). Answer: (a). Because the basketball player’s weight is distributed over the larger surface area of the shoe, the pressure (F / A) that he applies is relatively small. The woman’s lesser weight is distributed over the very small cross-sectional area of the spiked heel, so the pressure is high.

Question:

The centre of mass of a championship-level high jumper passes below the bar even though the jumper passes above the bar. How is this possible?

Answer:

The body is curved like a horseshoe “drapped” over the bar. So only part of the body is above the bar.

Question:

A light, uncharged metallic sphere suspended from a thread is attracted to a charged rubber rod. After it touches the rod, the sphere is repelled by the rod. Explain.

Answer:

The electric field due to the charged rod induces charges on near and far sides of the sphere. The attractive Coulomb force of the rod on the dissimilar charge on the close side of the sphere is larger than the repulsive Coulomb force of the rod on the like charge on the far side of the sphere. The result is a net attraction of the sphere to the rod. When the sphere touches the rod, charge is conducted between the rod and the sphere, leaving both the rod and the sphere like-charged. This results in a repulsive Coulomb force.

Question:

Charge is said to be quantized. What does it mean? Explain.

Answer:

Charge is quantized. This means that charge come certain units only. So the size of a charge can only be, 0, ±e, ±2e, ±3e …where e = 1.602 * 10-19 C is the value of the charge present on a proton.

Question:

What is Fourier analysis?

Answer:

The mathematician Fourier proved that any continuous function could be produced as an infinite sum of sine and cosine waves

Question:

A 20 dB sound is twice as intense as a 10 dB sound, explain it.

Answer:

No, the decibel measurement system is logarithmic. The 20 dB sound has ten times the intensity: ten times as many watts per square meter. A typical person perceives it as twice as loud.

Question:

Many traffic lights change when a car rolls up to the intersection. How does the light sense the presence of the car?

Answer:

Traffic light sensors work by measuring the change in inductance of a coil embedded under the road surface when a car drives over it.

Question:

Which is denser, dry air or air saturated with water vapor? Explain.

Answer:

The dry air is denser. Since the air and the water vapor are at the same temperature, they have the same kinetic energy per molecule. For a controlled experiment, the humid and dry air is at the same pressure, so the number of molecules per unit volume must be the same for both. The water molecule has a smaller molecular mass (18.0 u) than any of the gases that make up the air, so the humid air must have the smaller mass per unit volume.

Question:

Is it true that de Broglie wavelength associated with particles like protons and electrons only? Or it is applicable to larger things like baseballs also, explain it.

Answer:

No. The wavelengths of objects with relatively large momenta, such as moving baseballs, are so small that experiments do not reveal their wave-like properties. But these objects are still subject to the laws of quantum physics. For large objects moving at ordinary speeds, the predictions of quantum physics and those of Newtonian mechanics are identical for all intents and purposes, much as special relativity essentially agrees with Newtonian mechanics at slow enough speeds.

Question:

Is a black body black? Explain by giving solid reason.

Answer:

No. The "blackness" of a black body refers to its ideal property of absorbing all radiations incident on it. If a room-temperature object absorbs all radiation, we describe it as (visibly) black. The black appearance, however, is due to the fact that our eyes are sensitive only to visible light. If we could detect radiation with our eyes, we would see the object emitting radiation. If the temperature of the black body is raised, Wien's Law and Stefan's Las tell us that sufficient radiation will be emitted in the visible range for the object to glow visibly. Thus the black body could appear possibly as red, while, or blue, depending on its temperature

Question:

Two solid blocks of identical size are submerged in water. One block is lead and the other is aluminum. Upon which is the buoyant force greater?

Answer:

The buoyant force is the same on each, for both blocks displace the same volume of water. For submerged objects, only the volume of water displaced, not the object's weight, determines the buoyant force.