Quiz Chapter 7: Energy and Power

1. A worker pushes a crate with a constant horizontal force of $50 N$ across a smooth floor over a distance of $4 m$. How much work is done by the worker?

1. 12.5 J
2. 54 J
3. 200 J
4. 20 J

2. Calculate the gravitational potential energy possessed by a $2 kg$ book rested on a shelf $3 m$ above the floor ($g = 10 m s^-2$).

1. 6 J
2. 15 J
3. 30 J
4. 60 J

3. What is the S.I. unit for measuring Work ($W$)?

1. Joule (J)
2. Watt (W)
3. Newton (N)
4. Pascal (Pa)

4. An electric motor takes 4 seconds to perform 800 J of work. What is the power output of the motor?

1. 3200 W
2. 800 W
3. 400 W
4. 200 W

5. A simple pendulum swings back and forth between points A, B, and C (where B is the lowest point). At which position is its kinetic energy at a MAXIMUM?

1. At position A (highest left point)
2. At position B (lowest central point)
3. At position C (highest right point)
4. At both A and C

6. Using conservation of energy, calculate the velocity of a $0.5 kg$ ball dropped from a height of $5 m$ just before hitting the floor ($g = 10 m s^-2$).

1. $10 m s^-1$
2. $25 m s^-1$
3. $50 m s^-1$
4. $100 m s^-1$

7. A sports car of mass $1000 kg$ travels at a constant velocity of $20 m s^-1$. Find its kinetic energy.

1. 100,000 J
2. 200,000 J
3. 400,000 J
4. 20,000 J

8. A student weighing $450 N$ climbs a staircase of vertical height $4 m$ in $6 seconds$. What is the useful power generated by the student?

1. 1800 W
2. 300 W
3. 112.5 W
4. 675 W

9. In which of the following scenarios is NO work done according to physics definition?

1. Lifting a $5 kg$ box from the floor onto a table
2. Pushing a heavy concrete wall without moving it
3. Pulling a toy car across the floor
4. Climbing up a flight of stairs

10. A crane lifts a $500 kg$ load vertically upwards through a height of $10 m$ in $10 seconds$. Calculate the power generated by the crane (taking $g = 10 m s^-2$).

1. 500 W
2. 5000 W
3. 50000 W
4. 50 W