Question

1`A puck of mass 0.110 kg slides across ice in the positive x-direction with a kinetic friction coefficient between the ice and puck of 0.167. If the puck is moving at an initial speed of 15.0 m/s, find the following.

(a) What is the force of kinetic friction? (Indicate the direction with the sign of your answer.)
N

(b) What is the acceleration of the puck? (Indicate the direction with the sign of your answer.)
m/s²

(c) How long does it take for the puck to come to rest?
s

(d) What distance does the puck travel during that time?
m

(e) What total work does friction do on the puck?
J

(f) What average power does friction generate in the puck during that time?
W

(g) What instantaneous power does friction generate in the puck when the velocity is 4.00 m/s?
W

Answer 1

given that

m =  0.110 kg

kinetic friction coefficient between the ice and puck u_k = 0.167.

u = 15 m/s

(a)

F_k = u_k*N

N = m*g

F_k = u_k*m*g

F_k = 0.167*0.110*9.8

F_k = 0.180 N ( - x direcction)

(b)

we know that

F_k = -m*a

0.180 = -0.110*a

a = -1.63 m/s^2 (+x direction)

(c)

given v = 0

v = u+a*t

0 = 15-1.63*t

t = 9.20 s

(d)

s = u*t-1/2*a*t^2

s = 15*9.20 -0.5*1.56*9.20*9.20

s = 71.99 m

(e)

W = F_k*s

W = 0.180 *  71.99

W = 12.95 J

(f)

P = dW /dt = 12.95 / 9.20

P= 1.40 W

(g)

P = F*v

P = 0.180 *4

P = 0.72 W