The following two questions (14 and 15) pertain to a 200g hockey puck that is la

Question

The following two questions (14 and 15) pertain to a 200g hockey puck that is launched up a ramp inclined at a 30° angle above the horizontal. The coefficients of static and kinetic friction between the puck and the ramp are = 0.40 and ,-0.30, respectively, and the puck's initial velocity at the base of the ramp is 3.8m/s 14.) [3 points] How much time does it take for the puck to reach its highest point on the ramp (before it momentarily stops and begins sliding back down)? a.) 0.1s b.) 0.2s c.) 0.3s d.) 0.4s e.) 0.5s 15.) 13 oointsl What is the puck's acceleration as it slides back down the ramp? a.) 2.35m/s2, directed up the ramp b.) 2.35m/s', directed down the ramp c.) 4.90m/s2, directed down the ramp d.) 7.25m/s2, directed down the ramp e.) 7.25m/s2, directed up the ramp

Explanation / Answer

(a) accleration= a = -g(sin30 + µkcos) = -9.8(0.5+ 0.3*0.866)=-7.446 m/s^2

initial velocity= Vi=3.8 m/s

Vf= Vi+ at

0= 3.8 - 7.446(t)

t= 3.8/7.446 =0.5 seconds

(a) acceleartion down the ramp is given by  a = g(sin30 - µkcos) = 9.8(0.5-0.3*0.866)=2.35 m/s^2 directed down the ramp.

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