Collisions and Change in Momentum

AI Thread Summary
The problem involves a 4.7 kg ball moving at 1.9 m/s that collides with a wall and bounces back at the same speed in the opposite direction. The initial momentum is calculated as 8.93 kg·m/s in the positive x-direction, while the final momentum is -8.93 kg·m/s in the negative x-direction. The change in momentum is determined by subtracting the initial momentum from the final momentum, resulting in a total change of -17.86 kg·m/s. This negative value indicates that the change in momentum is directed toward the negative x-direction. The discussion emphasizes the importance of sign in momentum calculations.
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Homework Statement



A ball of mass 4.7 kg moving with speed of 1.9 m/s in the x-direction hits a wall and bounces back with the same speed in the -x-direction. What is the change of momentum of the ball? And in what direction?

Homework Equations



p=mv

The Attempt at a Solution



P=mv
P=4.7*1.9
P=8.93
 
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So what is the initial momentum?

What is the final momentum?

What is the difference?
 
The initial is 8.93 and the final is -8.93..so total momentum is 0? In what direction?
 
Try again using pf - pi to find the difference.
 
jabbie3 said:
The initial is 8.93 and the final is -8.93..so total momentum is 0? In what direction?

Sorry, signs matter.

Initial momentum = P
Final momentum = -P

Final - initial = Δ = (-P) - P = -2P

Negative because Δx/Δt is toward -x.
 

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