Question

A

170 g hockey puck sliding at 25 m/s slows to a speed of 10 m/s in a distance of
7.5 m.  Determine the force of friction
causing the puck to slow.  

Answer 1

From 2nd Newton Law:
F=ma
m=170g=0,17kg
Acceleration using kinematic equations:
vk²=vp²+2aΔd
vp-initial velocity=25m/s
vk-ending velocity=10m/s
Δd-distance
a=
`( vk^(2)- vp^(2) )/(2Δd)`
a=
`(100-625)/(2*7,5)`
a=
`(-525)/(15)`
a=-35
`(m)/(s)`²
F=0,17kg*(-35m/s²)=-5,95N