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Physics Questions:

A .0.40 kg soccer ball approaches a player horizontally with a velocity…

Complete Question Text:

A .0.40 kg soccer ball approaches a player horizontally with a velocity of 18 m/s to the north. The player strokes the ball and causes it to move in the opposite direction with a velocity of 22 m/s. what impulse was delivered to the ball by the player?

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Asked on Nov. 15, 2012, 5:58 p.m.
Isaac B. Tutors Physics + 16 others
Johns Hopkins University 2013 - Philosophy, Mathematics
9
"As early as elementary school, I was asked by my principal to help a fellow student who was struggling with math. In..."

To make a slight correction on Stephen's answer. Impulse is F*t, the force applied to something multiplied by how long the force is applied (or more generally the integral of F dt, but this needs not concern us). However, we know that the change in the momentum of a system is equal to the impulse added to the system: momentum is equal to m*v, where m is mass and v is velocity.

His calculation then works. We have a change in momentum of (v1-v0)(m)=18–(–22)(0.4)=40*0.4=16, so the impulse must be 16.

Just remember to distinguish the concepts of impulse and momentum, even though they coincide in practice.

Stephen C. Tutors Physics + 13 others
University of Notre Dame 2015 - Mechanical Engineering
1
"I have tutored throughout all of high school, in most science and math classes. I tutored over the summer, and will probably..."

Impulse is defined as the change in velocity multiplied by the mass of the object.
So our mass is 0.4 kg
our Initial velocity is 18 m/s
and our final velocity is 22 m/s in the OPPOSITE direction.
Therefor, our change in velocity is positive 18 m/s minus negative 22 m/s. Giving us a total change in velocity of 40 m/s

Multiply this by 0.4 kg, and we get an impulse of 40m/s * 0.4kg = 16 kg*m/s

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