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.  

From 2nd Newton Law:F=mam=170g=0,17kgAcceleration using kinematic equations:vk²=vp²+2aΔdvp-initial velocity=25m/svk-ending velocity=10m/sΔd-distancea=[tex] \frac{ vk^{2}- vp^{2} }{2Δd} [/tex]a=[tex] \frac{100-625}{2*7,5} [/tex]a=[tex] \frac{-525}{15} [/tex]a=-35[tex] \frac{m}{s} [/tex]²F=0,17kg*(-35m/s²)=-5,95N