# physics

posted by .

A racing dog is initially running at 20.0 m/s, but is slowing down.
Question: How fast is the dog moving when its kinetic energy has been reduced by half?
Question: By what fraction has its kinetic energy been reduced when its speed has been reduced by half?

• physics -

Use the fact that
kinetic energy = (1/2)MV^2.

For half the kinetic energy, the V^2 term must be reduced from 400 to 200, in this case.

That means V = 14.14 m/s

If you reduce speed by half, you have 1/4 the kinetic energy

## Similar Questions

1. ### physics

a racing dog is initially running at 10.0 m/s, but is slowing down. (a) How fast is the dog moving when its kinetic energy has been reduced by half?
2. ### physics

A racing dog is initially running at 15.0 m/s, but is slowing down.How fast is the dog moving when its kinetic energy has been reduced by half?
3. ### Physics kinetic energy

Okay the equation for kinetic energy is = 1/2mv^2 so how would i figure this out?
4. ### physics

A racing dog is initially running at 20.0 , but is slowing down. Q1. How fast is the dog moving when its kinetic energy has been reduced by half?
5. ### physics

What is the kinetic energy of a 15 kg dog that is running at a speed of 8.9 m/s (about 20 mi/h)?
6. ### physics

What is the kinetic energy of a 19 kg dog that is running at a speed of 7.7 m/s (about 17 mi/h)?
7. ### physics

What is the kinetic energy of a 15 kg dog that is running at a speed of 8.7 m/s (about 19 mi/h)?
8. ### Physics

You are walking a dog when the dog sees a cat and runs away from you. You immediately run after the dog at 4.20 m/s. You jump at an angle of 28.0° to try and catch the dog. While you are in the air the dog is able to move an extra …
9. ### Physics

You are walking a dog when the dog sees a cat and runs away from you. You immediately run after the dog at 4.90 m/s. You jump at an angle of 30.0° to try and catch the dog. While you are in the air the dog is able to move an extra …
10. ### Physics

You are walking a dog when the dog sees a cat and runs away from you. You immediately run after the dog at 5.50 m/s. You jump at an angle of 29.0° to try and catch the dog. While you are in the air the dog is able to move an extra …

More Similar Questions