# Which of the following objects has the greatest kinetic energy?

a baseball flying through the air at 90 miles per hour

a baseball flying through the air at 45 miles per hour

a baseball flying through the air at 20 miles per hour

a baseball sitting on the ground

Which of the following is true about high-energy mechanical devices?

They usually need to be kept warm in order to preserve mechanical energy.

They usually need to be cooled to dissipate thermal energy build-up and prevent damage.

They usually convert radiant energy into electrical energy.

During an energy conversion, none of the energy is transferred as thermal energy because the devices are free of friction.

A 0. 100-kilogram apple hangs in a tree 1. 50 meters above the ground. Ignoring frictional effects, the total mechanical energy of the apple is _____.

0. 00 J

less than 1. 47 J but more than 0. 00 J

exactly 1. 47 J

more than 1. 47 J

A 0. 100-kilogram apple falls from a height of 1. 50 meters to 1. 00 meters. Ignoring frictional effects, what is the kinetic energy of the apple at this height?

0. 00 J

0. 49 J

0. 98 J

1. 47 J

A CD player uses 1,200 joules of energy in 60 seconds. What is the power rating of the CD player?

72,000 W

600 W

20 W

0. 05 W

A gust of wind pushes a beach ball with a force of 9 newtons. The ball rolls 10 meters in 3 seconds. What is the power of the wind?

900 W

90 W

30 W

3 W

Thank you so much!!!:D

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- Which of the following objects has the greatest kinetic energy?
- A 0 100-kilogram apple falls from a height of 1 50 meters to 1 00 meter Ignoring frictional effects the total mechanical energy of the apple at this height is _____
- A 0 100-kilogram apple falls from a height of 1 50 meters to 1 00 meters Ignoring frictional effects what is the kinetic energy of the apple at this height?
- which object will have the greatest change in electrical energy
- A 0 100-kilogram apple falls from a height of 1 50 meters to 1 00 meter Ignoring frictional effects the total mechanical energy of the apple at this height is _____ 0 00 J less than 1 47 J but more than 0 00 J exactly 1 47 J more than 1 47 J
- Which of the following objects has the greatest kinetic energy

"Which of the following objects has the greatest kinetic energy?"

KE is (1/2)mv^2. They all have the same mass. So KE depends on velocity.

"Which of the following is true about high-energy mechanical devices?"

Just give a few seconds thought to each answer.

They usually need to be kept warm in order to preserve mechanical energy.

They usually need to be cooled to dissipate thermal energy build-up and prevent damage.

(Is it your experience that devices get cold and need warming, or get warm and need cooling?)

They usually convert radiant energy into electrical energy.

(Are the devices in your house driven by light?)

During an energy conversion, none of the energy is transferred as thermal energy because the devices are free of friction.

(Is there such a thing as a device free of friction?)

"A 0.100-kilogram apple hangs in a tree 1.50 meters above the ground. Ignoring frictional effects, the total mechanical energy of the apple is _____."

The potential energy is mgh. The kinetic energy is (1/2)mv^2. "Total mechanical energy" means the sum of those. The velocity is 0 since it's just hanging.

A 0.100-kilogram apple falls from a height of 1.50 meters to 1.00 meters. Ignoring frictional effects, what is the kinetic energy of the apple at this height?

It's equal to the change in PE from 1.5 meters to 1.0 meters. PE = mgh.

"A CD player uses 1,200 joules of energy in 60 seconds. What is the power rating of the CD player?"

Power means energy per unit time. You have the energy and the time.

"A gust of wind pushes a beach ball with a force of 9 newtons. The ball rolls 10 meters in 3 seconds. What is the power of the wind?"

The work (energy) done is F*d. Power is energy per unit time. You have the energy and the time.

Or you could use this formula: P = F*v which combines P = E/t and E = F*d.