The puck has a mass of 2.0 kg. Between the board and puck the coefficient of sta
ID: 2168317 • Letter: T
Question
The puck has a mass of 2.0 kg. Between the board and puck the coefficient of static friction is 0.35 and of kinetic friction is 0.25.
a) If she pushes the puck with force of 5.0 N in the forward direction, doe the puck move?
b) As she is pushing, she trips and the force in the forward direction suddenly becomes 7.5 M. Does the puck move?
c) If so, what is the acceleration of the puck along the board if she maintains contact between puck and stick as she regains her footing while pushing steadily with a force of 6.0 N on the puck?
d) She carries her game to the moon and again pushes a moving puck with a force of 6.0 N forward. Will the acceleration of the puck during contact be more, the same, or lass than on Earth? Explain.
Explanation / Answer
So in order to find the work done we'll need to find the difference in kinetic energies W=KEf-KEi The initial kinetic energy we can do right away. KE=(1/2)mv^2=(1/2)(.220 kg)(.65 m/s)=.072 J Right now the puck is drawn closer to the hole in the table by 15 cm. So it goes from 40 cm away to 25 cm away. This means it'll have a different angular momentum, luckily all that is conversed due to a lack of friction going on. Angular momentum=rmvSinx But because the radius and the direction of motion are right angles to one another we can say that angular momentum L=rmv so now we set it up such that L(initial)=L(final) due to conservation rmv(initial)=rmv(final) since the masses didn't change we may cancel them out rv(initial)=rv(final) We know the initial radius and velocity, and the final radius..just need to find the final velocity so we will solve for it. (Ri*Vi)/R(final)=V(final) V(Final)=(.40 m*.65 m/s)/.25 m=1.04 m/s which is faster than our original velocity, something we expected. Now that we know the new velocity we can calculate it's kinetic energy. KEf=(1/2)mv^2=(1/2)(.220 kg)(1.04 m/s)=.11 J So therefore W=KEf-KEi=.11J-.072 J=.042 J and that's your answer. Hope this helped!
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