Work and Energy (Grade 8)
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Work and Energy
Which of the following is NOT an example of kinetic energy being converted to potential energy?
- a basketball player jumping for a rebound
- releasing a compressed spring
- squeezing a rubber ball
- pulling a sled up a hill
Which one is doing the most work?
- pulling a box 10 m with a force of 100 N
- pushing a box 100 m with a force of 200N
- pulling a sled 1000 m with a force of 10N
- pushing a car with a force of 100000 N and it doesn't move
A 100kg rock is 100m above the ground, what is the potential energy of the rock?
An example of potential energy is:
- a basketball sitting on the rack
- a bird flying
- Grandma rocking in her chair
- none of the above
A car or truck moving down the highway has energy by virtue of its motion.
Kristopher carried a 200 Newton bag 3 meters up a ladder in 30 seconds. How much power did he use?
- 2000 Watts
- 18000 Watts
- 20 Watts
- 0 Watts
Which situation is an example of increasing potential energy?
- a bicyclist stopping at a stop sign
- a cat jumping from a tree
- emptying a bucket of water
- pulling a wagon uphill
An arrow in a bow has 70 J of potential energy. Assuming no loss of energy due to heat, how much kinetic energy will it have after it has been shot?
- 140 J
- 70 J
- 50 J
- 35 J
Imagine an object held at some height above the ground. It is released and falls toward the ground. Ignoring air resistance or friction, which of the following must be true?
- Before it falls, all of its energy must be potential energy
- At the end of its fall, all of its energy must be converted to kinetic energy
- During its fall, the combination of its kinetic and potential energy must equal the amount of potential energy with which it started
- All of the above
An object with the mass of .1 kg was dropped from a cliff 200 m high. Immediately before hitting the ground, it was clocked to travel with the speed of 40 m/s. Calculate how much energy was dissipated by the air drag.