# physics

posted by .

A 29 kg child, with a 4.5 kg backpack on his back, first stands on a sidewalk and then jumps up into the air. Find the magnitude and direction of the force on the sidewalk from the child when the child is (a) standing still and (b) in the air. Now find the magnitude and direction of the net force on Earth due to the child when the child is (c) standing still and (d) in the air.

• physics -

total mass = 33.5kg
total force = 9.8 * 33.5

when standing, that's it.
in the air, no force

on earth, force is the same when standing
in the air, F = GmM/r², so it depends on how high he can jump.

## Similar Questions

1. ### Physics

How do I do these? A passenger at an airport steps onto a moving sidewalk that is 100.0 m long and is moving at a speed of 1.5 m/s. The passenger then starts walking at a speed of 1.0 m/s in the same direction as the sidewalk is moving.
2. ### Physics

A child bounces a 55 g superball on the side- walk. The velocity change of the superball is from 22 m/s downward to 14 m/s upward. If the contact time with the sidewalk is 1 800 s, what is the magnitude of the average force exerted …
3. ### Physics

A child bounces a 46 g superball on the side-walk. The velocity change of the superball isfrom 28 m/s downward to 16 m/s upward.If the contact time with the sidewalk is1800s, what is the magnitude of the average forceexerted on the …
4. ### Physics Momentum

A child bounces a 49 g superball on the side- walk. The velocity change of the superball is from 27 m/s downward to 12 m/s upward. If the contact time with the sidewalk is 1 800 s, what is the magnitude of the average force exerted …
5. ### Physics

a 0.2kg rubber ball is dropped from the window of a building. It strikes the sidewalk below at 30 m/s and rebounds up at 25 m/s. If the ball is in contact with the sidewalk for 0.025s, what is the magnitude of the average force applied …
6. ### Physics

a 0.2kg rubber ball is dropped from the window of a building. It strikes the sidewalk below at 30 m/s and rebounds up at 25 m/s. If the ball is in contact with the sidewalk for 0.025s, what is the magnitude of the average force applied …
7. ### physics

A child bounces a 54 g superball on the side- walk. The velocity change of the superball is from 23 m/s downward to 19 m/s upward. If the contact time with the sidewalk is 1 800 s, what is the magnitude of the average force exerted …
8. ### physics

a child bounces a superball on the sidewalk. The velocity change of the superball is from 23m/s downward to 14m/s upward. if the contact time with the sidewalk is 1/800s, what is the magnitude of the average force exerted on the superball …
9. ### Physics

A 33.4 kg child, with a 3.05 kg backpack on his back, first stands on a sidewalk and then jumps up into the air. Find the force (positive up/negative down) on the sidewalk from the child when the child is (a) standing still and (b) …
10. ### Physics

A 23.7 kg child, with a 4.35 kg backpack on his back, first stands on a sidewalk and then jumps up into the air. Find the net force (positive up/negative down) on Earth due to the child when the child is (c) standing still and (d) …

More Similar Questions