Quick Question - Conservation of Momentum

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The discussion revolves around calculating the change in momentum of a ball with a mass of 0.10 kg that strikes a wall and bounces back. Initially, the ball has a momentum of 0.70 kg m/s (0.10 kg x 7 m/s) before impact and a momentum of -0.40 kg m/s (0.10 kg x -4 m/s) after bouncing back. The change in momentum is calculated by subtracting the final momentum from the initial momentum, resulting in a total change of 1.1 kg m/s. The initial confusion regarding the calculation led to a miscalculation of 0.30 kg m/s. Ultimately, the correct change in momentum is confirmed to be 1.1 kg m/s.
Dooga Blackrazor
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ball with a mass of 0.10 kg has a velocity of 7 m/s. It strikes a concrete wall perpendicularly and bounces straight back with velocity of 4 m/s. The change in the ball's momentum was equal to

Response Answer Choices
a. 0.30 kg m/s
b. 0.10 kg m/s
c. 0.40 kg m/s
d. 1.1 kg m/s

0.1 x 7 and .4 x .1 = .7 and .4 and subtracting them gives .30 kg m/s, correct?
 
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Nevermind, I found the answer (1.1). Silly mistake.
 

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