Work

Q.

Under what conditions is the work done i) maximum and ii) minimum?

Q.

Under what condition is the work done by a force equal to zero?

1. when the object moves perpendicular to force.
2. when the object does not move.

1. Only A

2. Only B

3. Both A and B

4. Neither A and B

Q.

The work done by a pendulum after a complete oscillation is

1. zero

2. equal to potential energy of the pendulum.

3. equal to kinetic energy of the pendulum

4. equal to total energy of the pendulum

Q.

In a tug of war, will the work done by a winning team be positive or negative?

Q.

When a force acting on a body displaces it in the direction of force, the work done by the force is

1. minimum

2. maximum

3. zero

4. infinite

Q.

Define 1 joule of work.

Q.

The work done by a force depends on

1. force

2. displacement

3. velocity

4. angle between force and displacement

Q.

In a tug of war, one team wins, and the other team losses. Which team does positive work and which one does negative work? justify your answer.

Q.

When the displacement $\left(S\right)$ is in the direction of the force $\left(F\right)$, work done is equal to ______.

Q.

How much the work is done when the earth moves around the sun in its orbit.

Q.

State the work done in the following situations:

A person carrying bricks on his head on a level road from one place to another.

Q.

No work is done when we push immovable objects like a huge stone or a wall etc. However, we feel tired in doing so. Explain why?

Q.

In which case work is not done:

1. a girl swimming in a pond

2. a windmill lifting water from a well

3. a standing man holding a suit case in his hand

4. a sail boat moving in the direction of wind

Q.

Define the physical concept of the work with some examples. [2 MARKS]

Q. Distinguish between potential energy and kinetic energy of a body.

Q.

A force of $80N$ displaces an object through $5m$ in the direction of force. Calculate the work done.

Q.

A force of $20\mathrm{N}$ acts on a body and the body moves through $1\mathrm{m}$ at an angle of $45°$ to the direction of the force. The work done by the force is

1. $10\sqrt{2}\mathrm{J}$

2. $\frac{10}{\sqrt{2}}\mathrm{J}$

3. $-10\sqrt{2}\mathrm{J}$

4. $\frac{-10}{\sqrt{2}}\mathrm{J}$

Q.

Write an expression for the work done when a force is acting on an object in the direction of its displacement.

Q. A machine lifts up a load of $500kg$ by a height of $2m$. Calculate the efficiency of the machine if the energy input to the machine is $25000J$. (Take $g=10m{s}^{-2}$).

1. 0.4

Q. Select the cases in which work done is not zero.

1. A bird flying
2. A kid standing at a bus stop
3. A man pushing a wheelchair
4. A bike at a parking spot

Q. Work done on an object does not depend on the:

1. Displacement (d)
2. Angle between Fand d
3. Force (F)
4. Initial velocity of the object

Q.

If two people are pulling a box in the same direction with a force of 85 N and 65 N each respectively and the net displacement of that box due to this force is 18 m, then find the net work done.

1. 2700 J

2. 1900 J

3. 2800 J

4. 1250 J

Q.

A flying bird in the sky is at rest.

1. True
2. False

Q.

A force of 5 N is used to displace a block by 5 m in the first case and by 2.5 m in the second case. If the work done is W and W’ respectively, the relation between W and W’ is

1. W < W’

2. W = W’

3. W > W’ or W < W’ depending on final velocity of the block

4. W > W’

Q.

Write an expression for work done when force is acting on an object at an angle to displacement.

Q. We require _____ to do work.

1. speed
2. energy
3. mass
4. weight

Q.

Vijay is pulling a block with 22 N force and Gopal is pulling it with 10 N force in opposite direction. Vijay is able to pull the block towards himself for a total distance of 6.5 m. Find the net work done.

1. 12 J

2. 78 J

3. 90 J

4. 85 J

Q. The expression for work done, when the displacement is in the direction of the force is:

1. $F\times S$
2. $0$
3. $-\frac{F}{S}$
4. $\frac{F\times S}{2}$

Q.

Choose the correct option according to the angle between force and direction of displacement.

$$\begin{array}{cc}\text{Coloumn 1}& \text{Coloumn 2}\\ \text{1.}\theta \text{is zero}& \text{i) Work done is always zero}\\ 2.\theta \text{is less than}{90}^0& \text{ii)Work done is non-negative}\\ 3.\theta \text{is greater than}{90}^0& \text{iii) Work done is always positive}\\ 4.\theta \text{is}{90}^0& \text{iv) Work done is never positive}\end{array}$$

1. 1-ii, 2-ii, 3-iv, 4-i

2. 1-iii, 2-iii, 3-iv, 4-i

3. 1-iii, 2-ii, 3-iv, 4-i

4. 1-ii, 2-ii, 3-i, 4-iv

Q. What is the SI unit of work done?

1. Joule
2. Newton
3. Watt
4. Ampere