Year 12s: what will be the first way you research your future options? >>

2 questions

1- How does hitting a rug with a tennis racket help clean it? Explain using Newton's Laws.

2-Is it possible for an object to be moving in one direction while the net force acting on it is in another direction? again, some sort of explanation would be helpful.

Reply 1

Stonebridge

Original post by PatchworkTeapot

1) Maybe you could tell us if you have any thoughts on this yourself, first.
2) Throw a ball upwards. It moves up but the force of gravity on it (its weight) acts in a downwards direction. Can you think of any other examples?

Reply 2

PatchworkTeapot

For the first one, I'm pretty sure it has to do with Newton's 3rd law and the force in the opposite direction, I'm just not sure how to explain it.
2- While the ball is moving up, doesn't it still have a net force in the upward direction until it starts to fall?

Reply 3

Stonebridge

Original post by PatchworkTeapot

For the first one, I'm pretty sure it has to do with Newton's 3rd law and the force in the opposite direction, I'm just not sure how to explain it.

I think it's more to do with the inertia of the dust...

2- While the ball is moving up, doesn't it still have a net force in the upward direction until it starts to fall?

Definitely not. What possible force would that be once the ball has left your hand?

In any situation where an object is moving and decelerating, the resultant force on it is in the opposite direction to the motion. That's why the object is slowing down and not getting faster.
So just applying the brakes on a moving car produces just this situation.

Reply 4

PatchworkTeapot

I'm still not 100% sure how to explain the answer for the second question.

Reply 5

Stonebridge

Original post by PatchworkTeapot

I'm still not 100% sure how to explain the answer for the second question.

The question asks is it possible. The answer is yes.
I've given you two examples in my posts.
Acceleration is always in the direction of the resultant force. If the force is in the opposite direction to the motion, then the acceleration is in the opposite direction to the motion. The two examples illustrate this.
Acceleration in the opposite direction to motion (negative acceleration) is the same thing as deceleration.

(edited 10 years ago)