Answer to Question #157396 in Optics for clara

Question

A hockey bag (m = 18 kg) is dragged across the arena floor by a hockey player who applies a horizontal force of 99 N against a kinetic friction force of 87 N.

a) Calculate the work done on the hockey bag over a displacement of 9 m.

(i) By the hockey player.

(ii) By the force of kinetic friction.

b) Calculate the net (total) work done on the hockey bag.

c) Calculate the change in the kinetic energy (ΔEK) of the hockey bag. 

Answer 1

a)

(i) Let's calculate the work done by the hockey player:

$$W_{player}=F_{h}d=99\ N\cdot9\ m=891\ J.$$

(ii) Let's calculate the work done by the force of kinetic friction:

$$W_{fr}=F_{fr}d=87\ N\cdot9\ m=783\ J.$$

b) Let's calculate the net (total) work done on the hockey bag:

$$W_{net}=F_{net}d=(99\ N-87\ N)\cdot9\ m=108\ J.$$

c) The change in kinetic energy of the hockey bag euals to the net work done on the hockey bug:

$$\Delta KE=W_{net}=108\ J.$$