Question: 1 . The difference between work and power is that: An object must move for work to be done, but not for power to be
1.The difference between work and power is that:
- An object must move for work to be done, but not for power to be exerted Work is always larger than power
- Time is not important to determine the work done, but it is for the power exerted
- They are exactly the same thing
2. At which point would a skateboarder have the most kinetic energy?
- At rest at the top of a half-pipe, just before gliding down the ramp.
- At the very bottom of the half-pipe, after gliding down.
- On his way back up the far side of the half-pipe
- His kinetic energy would be the same everywhere
3. What is FALSE about the binder(972 g) and the calculator(241 g) sitting on your desk?
- Both have the same amount of gravitation potential energy.
- Both have the same amount of kinetic energy.
- If they fall off the desk, both with hit the floor at the same speed.
- B and C are both False
4. Melika used 686 N of force to hold her body in the bottom of a push-up position 25 cm above the ground, for 30 seconds. How much work did Melika do?
- 5.7 J
- 170 J
- 17000 J
- None
5. Which unit below is NOT a possible unit for power?
- W
- Nm/s
- J/min
- N/s
6.In which of the following cases is work NOT being done?
| A) | holding a watermelon at chest height |
| B) | pushing a bicycle 0.2 km [E] |
| C) | walking down a flight of stairs |
| D) | playing a guitar solo |
| E) | coasting to a stop on ice skates |
7.Which of the following is NOT an expression for energy?
| A) | B) | C) | D) | E) |
8.Two boys have the same mass and are riding on identical bicycles. One boy has a speed of
8 m/s and the other a speed of 2 m/s. What is the ratio of the first boy's kinetic energy to the second boy's kinetic energy?
| A) | 16:1 | B) | 8:1 | C) | 4:1 | D) | 2:1 | E) | 1:1 |
9. A force F acting on a stationary block on a smooth level surface moves the block a horizontal displacement d in a time t. The power is
| A) | C) | zero | E) | ||
| B) | D) |
10.The sum of an object's gravitational potential energy and kinetic energy is called its
| A) | conserved energy | B) | stored energy | C) | total mechanical energy | D) | thermal energy |
11.Which of the following is equal to 1 joule (1 J)?
| A) | 1 N/kg | B) | 1 N m | C) | 1 N/s | D) | 1 W/s |
12.In which case is negative work being done?
| A) | forward force is applied to a forward moving soccer ball to increase its speed in that direction. |
| B) | The work done by the Earth on a ball as the ball, initially at rest, falls 3.0 m down towards the Earth. |
| C) | The work done by the friction to slow a sled as it slides along the snow. |
| D) | A cart is moving at a constant velocity of 5.7 m/s [N] when a 0.5 N [downward] force is applied. |
13. The energy "lost" pushing a box across a rough surface is transformed mostly into
| A) | friction | B) | kinetic energy | C) | potential energy | D) | thermal energy |
14.The speed of an object is doubled. The kinetic energy is
| A) | the same | B) | half () | C) | double () | D) | quadruple () |
15.Which of the following is NOT an expression for energy?
| A) | B) | C) | D) | E) |
16.A 6.0kg object moving at 12.0m/s at a height of 3.0m above the ground has a kinetic energy of
| A) | 432.0 J | B) | 176.6 J | C) | 608.6 J | D) | 255.4 J | E) | 72.0 J |
17. A 1400W motor uses 21kJ of energy to give a car 16kJ of kinetic energy. The efficiency of the motor is
| A) | 24% | B) | 31% | C) | 76% | D) | 131% | E) | 69% |
18. The engine of a truck moving at 11.0m/s exerts 2100N of force. The power output of the engine is
| A) | 23.1 kW | B) | 190.9 kW | C) | 23.1 W | D) | 231.0 W | E) | 2111.0 W |
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