Work Done in Different Frames of Reference

Q.

In which situation is no work done?

Q. If a person is pushing a box inside a moving train, the work done in the frame of earth will be:
${\overrightarrow{S}}_0=$ displacement of the train relative to ground.
$\overrightarrow{S}=$ displacement of the box w.r.t. train.

1. Zero
2. $\overrightarrow{F}.(\overrightarrow{S}+{\overrightarrow{S}}_0)$
3. $\overrightarrow{F}.{\overrightarrow{S}}_0$
4. $\overrightarrow{F}.\overrightarrow{S}$

Q.

Work is always done on a body when it experiences an increase in energy through a mechanical influence.

1. True
2. False

Q. A block of mass $10\text{kg}$ pulled by force $100\text{N}$. It covers a distance $500\text{m}$ in $10s$. From initial point this motion is observed by two observers $A$ and $B$ as shown in fig.



Find out work done by force $F$ in 10 seconds w.r.t. $A$ and $B$ respectively.

1. $5000\text{J}$ and $0$
2. $4000\text{J}$ and $0$
3. $5000\text{J}$ and $5000\text{J}$
4. $0$ and $6000\text{J}$

Q.

Does work has a direction associated with it?

Q.

When force acts on a body and if position of the object __________ it is said work is done.

Q.

What is the difference between scientific concept of work and our perception of work done in day to day life?

Q.

Are work and energy independent quantities?

Q.

Consider a scenario where a bus is moving with a constant speed. A person inside the bus, started pushing the bus from inside. Which of the following statements are true.

1. With respect to a person at rest(outside the bus) work is being done by the person pushing the bus.

2. No work is being done by the person in all frames of reference

3. With respect to a person in the bus(moving with same speed as that of the bus), no work is being done by the person pushing the bus.

4. Since the person is applying force, he is doing work

Q.

No mechanical work is done in holding a heavy bucket in one hand.

1. True
2. False

Q.

Whenever a force is applied on a body, work is done.

1. True
2. False

Q.

Give some examples where work done is zero.

Q.

Radha is holding a pot, filled with water, on her head and is standing at a place. Is she doing some work?

Q. Work done is dependent on frame of reference.

1. False
2. True

Q. Assertion :Work done by a conservative force is path independent. Reason: All constant forces are conservative in nature.

1. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
2. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.
3. Assertion is correct but Reason is incorrect.
4. Assertion is incorrect but Reason is correct.

Q. A block of mass 10 kg, moving in x direction with a constant speed of 10 $m{s}^{-1}$, is subjected to a retarding force F = $0.1xJ/m$ during its travel from x = 20 m to 30 m. Its final KE will be:

Q. A uniform rod of mass M and length L is pivoted at point A. It is struck by a horizontal force which believers delivers an impulse J at a distance x from point A as shown in figure, such that the impulse delivered by pivot is zero. If the angular velocity of the rod just after the impulse given is $\frac{6J}{nML}$. Find the value of n

1. $\frac{12J}{M{L}^2\omega }$
2. $0$
3. $\frac{18J}{M{L}^2\omega }$
4. $\frac{72J}{M{L}^2\omega }$

Q.

Differentiate work and energy

Q.

Look at the activity listed below. Reason out whether or not work is done in the light of your understanding of the term ‘work’.

An engine is pulling a train.

Q.

Consider a scenario where a bus is moving with a constant speed. A person inside the bus, started pushing the bus from inside. Which of the following statements are true.

1. With respect to a person at rest(outside the bus) work is being done by the person pushing the bus.

2. No work is being done by the person in all frames of reference

3. With respect to a person in the bus(moving with same speed as that of the bus), no work is being done by the person pushing the bus.

4. Since the person is applying force, he is doing work

Q. Define conservative forces.