Asked by sarah

the speed of the fastest pitched baseball was 45 m/s, and the ball's mass was 145 g. (a) What was the magnitude of the momentum of this ball, and how many joules of kinetic energy did it have? (b) How fast would a 57 gram ball have to travel to have the same amount of (i) kinetic energy and (ii) momentum
Answered by bobpursley
I will be happy to check your work.
Answered by sarah
P initial=(145g)*(45 m/s)
=6525 g*m/s

F= 0-6525/1.0s
= -6525N

This is part A
Answered by bobpursley
Normally, you should not use non-standard units, such as grams. Most used kg, which makes momentum kg*m/s
So that makes your calculations wrong, if you don't change g to kg, because you list it in Newtons (Newton=kg*m/s)
Answered by sarah
ok, so I will change g to kg.
And for part b, just plug in the different mass into the equation and solve for momentum and KE?
Answered by bobpursley
No, put in the different mass, the unknown velocity equalling the same momentum (or energy) as before. You are looking for the new speed for the heavier ball.
Answered by zoe
How fast does a 142-gram baseball have to be traveling to achieve a momentum of 3.905 kg m/s?
Answered by Adam Brown
27.5 m/s
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