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# Physics Specimen paper set 2 question watch

1. Explain, with reference to the conservation of momentum, the effect that themotion of the golf ball has on the motion of the Earth from the instant it is releaseduntil it bounces at the plate.

As ball falls momentum of ball toward the Earth (always) =momentum of Earth toward the ball

On impact the momentum of both ball and Earth becomezero

After impact momentum of ball away from Earth =momentumof Earth in opposite direction

I don't understand the first answer point thingy.

How does the momentum of the ball as it falls equal the momentum of the earth towards the ball?

I understand that when they impact their speed falls quickly to zero hence their momentums are zero. I understand that momentum is conserved hence the third point. Its just the first point I dont understand!

My understanding of the conservation of momentum is that m1u1 + m2u2 = m1v1 + m2v2.

I also know that the change in momentum is 0.5Ns (from previous part) so this means that there is a transfer of momentum to the earth by the ball? is this correct or is it nonsense lol.

Pls help with the first answer point!
2. The gravitational force of the earth on the ball causes the ball to accelerate downwards and gain momentum. Now, Newton's 3rd law states that for every action there is an equal and opposite reaction. So there is also an equally strong force on the earth from the ball in the opposite direction. (We just don't appreciate that there is a movement of the earth caused by the gravitational pull of the ball on the earth because it is so massive in comparison to the ball, the acceleration of the earth towards the ball is tiny.)
3. (Original post by Teenie2)
The gravitational force of the earth on the ball causes the ball to accelerate downwards and gain momentum. Now, Newton's 3rd law states that for every action there is an equal and opposite reaction. So there is also an equally strong force on the earth from the ball in the opposite direction. (We just don't appreciate that there is a movement of the earth caused by the gravitational pull of the ball on the earth because it is so massive in comparison to the ball, the acceleration of the earth towards the ball is tiny.)
Thank you!

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