A string is attached to each puck and the string is pulled with a constant force

Question

A string is attached to each puck and the string is pulled with a constant force. The string is wound around the outer edge of puck 2, but attached to the center of puck 1.

They both start from rest

1. Each puck moves a distance d in the time that you pull on the rope. In this case, the work done in the center of mass system is FTd. Is this work (FTd) also the total change in kinetic energy insituation 1?

A). yes

B). no

2. Each puck moves a distance d in the time that you pull on the rope. In this case, the work done in the center of mass system is FTd. Is this work (FTd) also the total change in kinetic energy insituation 2?

A). yes

B). no

Please explain why, thank you

Explanation / Answer

1) YES

beacause force is applied on centre of the puck. there is no chance to rotate.

( if puck wants to rotare, torque is requred. but here torque is zero about centre of the puck)

accroding to the theory,

work done = change in kinetic energy

so work done in the centre of mass system is equal to total change in kinetic energy.

2) NO

2nd case, force is applied top of the puck.force creates a tourqe.

tourqe= Fd * r (r- radius of the puck)

due to this tourqe, system will rotate. therefore rotaional energy is produced.

for this case,

work done = change in (kinetic energy + rotational energy)

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.