Question

At the local hockey rink, a puck with a mass of 0.12 kg is given an initial speed of 6.7 m/s .

Part A

If the coefficient of kinetic friction between the ice and the puck is 0.15, what distance does the puck slide before coming to rest?

Express your answer using two significant figures.

Part B

If the mass of the puck is doubled, does the frictional force F exerted on the puck increase, decrease, or stay the same?

Part C

Explain.

Part D

Does the stopping distance of the puck increase, decrease, or stay the same when its mass is doubled?

Part E

Explain

Part F

For the situation considered in part (a), show that Fd=12mv2. (The significance of this result will be discussed in Chapter 7 in the textbook, where we will see that 12mv2 is the kinetic energy of an object.)

Answer 1

Given,

• Mass of the puck = m = 0.12 kg
• Initial velocity of the puck = u = 6.7 m/s.
• coefficient of kinetic friction =

part (a)

coefficient of kinetic friction between the puck and the ice =

Puck is finally at rest, therefore the Final velocity of the puck = v = 0 m/s.

Friction force on the puck =

Let 'a' be the acceleration of the puck.

From the puck,

Hence the acceleration of the puck is 1.47 m/s^2. and nature is of deacceleration, due to making the final velocity of the puck zero.

From the kinematics,

Hence the distance traveled by the puck is 15 m.

Part (b)

Increases,

If the mass of the puck is doubled, the friction force acting on the puck will also be doubled, i.e. increases.

Part (c)

Friction force acting on the puck if the mass is doubled, i.e. M = 2m

Hence the friction force acting on the puck while the mass is doubled is 0.35 N.

Part (d)

Stay the same.

Friction force acting on the puck =

Now only the friction force is acting on the puck.

Hence the acceleration, initial and final velocities of the puck are the same as above, the distance traveled by the puck is also the same, because the distance traveled by the puck is independent of its mass.