Zero Work

Q.

The formula of work done is equal to _______.

Q. A man weighing $50\text{kg}$ is walking on a horizontal surface (assumed smooth) for a distance of $1\text{km}$. What is the work done by his weight?

1. Zero
2. Nothing can be said
3. Positive
4. Negative

Q. At the point of contact, work done by the normal reaction when a person climbs up the stairs is

1. Zero
2. Positive
3. None of these
4. Negative

Q. What is work done by the force of tension$\left(T\right)$ in the string of a simple pendulum?

1. $TL$
2. Zero
3. $\frac{TL}{4}$
4. $\frac{TL}{2}$

Q.

A block suspended from a vertical spring is in equilibrium. Show that the extension of the spring equals the length of an equivalent simple pendulum, i.e., a pendulum having frequency same as that of the block.

Q.

A boy holds a 40N weight at arm’s length for 10s. His arm is 1.5m above the ground, the work done by the boy on the weight while holding it is… [Take g=10 m/s^2]

1. Zero

2. 6.1J

3. 40J

4. 90J

Q.

A force is conservative if

Q. A block of mass $m$ is sliding down on a fixed inclined plane with velocity of $2\text{m/s}$ for a distance of $2\text{m}$. Angle of inclined plane is ${35}^{\circ }$. Calculate the work done by normal reaction on the block.

1. $0.5mg\sin {35}^{\circ }$
2. $0.5mg\cos {35}^{\circ }$
3. $2mg$
4. $0$

Q.

What is the work done by a planet revolving around the Sun?

Q.

A 1 kg block situated on a rough incline is connected to a spring of spring constant 100 N m^–1 as shown in Fig. 6.17. The block is released from rest with the spring in the unstretched position. The block moves 10 cm down the incline before coming to rest. Find the coefficient of friction between the block and the incline. Assume that the spring has a negligible mass and the pulley is frictionless.

Q. A ball is connected to a rope and swung around in uniform circular motion. The tension in the rope is measured at 10 N and the radius of the circle is 1 m. How much work is done in one revolution around the circle?

1. 1
2. 0 (No Work)
3. 2
4. 3

Q. A man weighing $50\text{kg}$ is walking on a horizontal surface (assumed smooth) for a distance of $1\text{km}$. What is the work done by his weight?

1. Zero
2. Positive
3. Negative
4. Nothing can be said

Q.

A body moves a distance of $10m$ along a straight line under action of $5N$ force. If work done is $25J,$ then the angle between the force and direction of motion of the body will be

1. $75°$

2. $60°$

3. $45°$

4. $30°$

Q.

A body of mass m is moving along the circular track of radius r with a constant speed v. The force on the body is $\frac{m{v}^2}{r}$ and is directed towards the centre. The work done by this force in moving the body over half the circumference of the circle is

1. $\frac{m{v}^2}{r}\times \mathrm{\pi r}$

2. $\frac{m{v}^2}{{\mathrm{\pi r}}^2}$

3. $\frac{{\mathrm{\pi r}}^2}{m{v}^2}$

4. zero

Q. What Is the sign of work done by pseudo force ?
positive or negative or zero

Q.

Name the type of friction that comes into play during skiing.

Q. A man weighing $50\text{kg}$ is walking on a horizontal surface (assumed smooth) for a distance of $1\text{km}$. What is the work done by his weight?

1. Zero
2. Positive
3. Negative
4. Nothing can be said

Q. An imaginery force $\overrightarrow{F}=\overrightarrow{B}\times \overrightarrow{V}$ given as the cross product of vector $\overrightarrow{B}$ (Force field) and $\overrightarrow{V}$ (velocity). Then the work done by the force is

1. Always equal to zero
2. Always less than zero
3. Always greater than zero
4. Can have any finite value

Q. At the point of contact, work done by the normal reaction when a person climbs up the stairs is

1. Positive
2. Negative
3. Zero
4. None of these

Q. At the point of contact, work done by the normal reaction when a person climbs up the stairs is

1. Positive
2. Negative
3. Zero
4. None of these

Q.

The sign of work done by a force on a body is important to understand. State carefully if the following quantities are positive or negative:

(a) work done by a man in lifting a bucket out of a well by means of a rope tied to the bucket.

(b) work done by gravitational force in the above case,

(c) work done by friction on a body sliding down an inclined plane,

(d) work done by an applied force on a body moving on a rough horizontal plane with uniform velocity,

(e) work done by the resistive force of air on a vibrating pendulum in bringing it to rest.

Q. When a stone tied to a string is whirled in a circle, the work done on it by the string is

1. Positive
2. Negative
3. Zero
4. Undefined

Q. A crane lifts a mass of $100kg$ to a height of $10m$ in $20s$. The power of the crane is (Take $g=10m{s}^{-2})$.

1. $100W$
2. $200W$
3. $250W$
4. $500W$

Q. A block of mass 10 kg is moving in x-direction with a constant speed of 10 m/s. It is subjected to a retarding force F=-0.1 xJ/m during its travel from x=20m to x=30m. Its final kinetic energy will be

1. 475 J
2. 450 J
3. 275 J
4. 250 J

Q. A box of mass $5$kg is kept inside a lift. Lift starts from rest and moves upward at a speed of $1m{s}^{-1}$. What is work done by normal force in first $5s$? $[g=10m{s}^{-2}]$

Q.

A truck moves at a steady speed on a horizontal road. What is the work done by the road on the truck?

Q.

A Man moves on a straight horizontal road with a block of 2kg in his hand. If he covers a distance of 20m with constant velocity of 1m/s. Find work done by man on block during motion.

1. 400J

2. 40J

3. zero

4. -10J

Q.

A body moves a distance of 10 m along a straight line under the action of a force of 5 N. If the work done is 25 joule, the angle which the force makes with the direction of motion of the body is

1. $0^{\circ }$

2. ${30}^{\circ }$

3. ${60}^{\circ }$

4. ${90}^{\circ }$

Q. A rod of length $l$ and mass $m$ hinged at one end is released from rest from vertical position as shown. The angular velocity of the rod in the position shown is:

1. $\frac{g}{l}$
2. $\frac{g}{l}\sin \theta$
3. $\sqrt{\frac{3g\cos \theta }{l}}$
4. $\sqrt{\frac{6g{\sin }^2\left(\theta /2\right)}{l}}$

Q. What is work done by the force of tension$\left(T\right)$ in the string of a simple pendulum?

1. $\frac{TL}{4}$
2. $\frac{TL}{2}$
3. $TL$
4. Zero