# a hockey player shoots a 150g puck at 40.0m/s from rest on a large flat ice lake. The hockey sticks is in contact with the puck over 70.0 cm and the puck eventually comes to rest 200m away. a...

a hockey player shoots a 150g puck at 40.0m/s from rest on a large flat ice lake. The hockey sticks is in contact with the puck over 70.0 cm and the puck eventually comes to rest 200m away.

a Determine the average force the hockey player applied to the puck(in N)

b Determine the average force of friction of the ice(in N)

c determine the coeffecient of friction of the ice

d using the conservation of energy, determine the speed of the puck after it has travelled 80.0m (in m/s)

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### 1 Answer

mass of the puck=150 gram=.15 kg

u=initial velocity=0 m/s

v= final velocity= 40 m/s

s= 200 m

Let total K.E used in doing work.

work done=`(1/2)m(v^2-u^2)`

`=.5xx.15xx(40^2-0)`

`=120 J`

a. As long as hockey stick was in contact ,work done.Hockey was in cntact for 70 cm

displacemet=.70 m

workdone= Force x displacement

`120=Fxx.70`

`F=120/.7=171.43N`

2.Now initial velocity =40 m/s

final velocity=0

distance travelled=200-.70=199.30m

average force of friction= F/distance

=171.43/199.30=.86 N/m

c. coefficient of friction

F= mu x mass of puck x g

171.43= mu x .15 x 22/7

coefficient of friction mu=363.64

d. s= 80.0 m

u= 40m/s

let velocity at at point when puck covered dstance 80m be v

energy at initial pont =energy at distance of 80m

120=.15 x a x 80

a=10m/s^2

Thus

`v^2=u^2+2as`

`=40^2+2xx10xx80`

`v=56.57` m/s