A 0.91-kg block is held in place against the spring by a 38-N horizontal externa
ID: 1389199 • Letter: A
Question
A 0.91-kg block is held in place against the spring by a 38-N horizontal external force (see the figure). The external force is removed, and the block is projected with a velocity v 1 = 1.2 m/s upon separation from the spring. The block descends a ramp and has a velocity v 2 = 1.7 m/s at the bottom. The track is frictionless between points A and B. The block enters a rough section at B, extending to E. The coefficient of kinetic friction over this section is 0.24. The velocity of the block is v 3 = 1.4 m/s at C. The block moves on to D, where it stops. The height h of the ramp is closest to
A)7.3 B) 7.4 C) 15 D) 11 E) 13Explanation / Answer
mass of block = 0.91kg
energy at top = KE of block + PE due to height of ramp
= 0.5*0.91*1.2^2 + 0.91*9.81*h
KE at bottom = 0.5*0.91*1.7^2
This energy should be same as total energy so
0.5*0.91*1.2^2 + 0.91*9.81*h = 0.5*0.91*1.7^2
0.6552 + 8.9271*h = 1.31495
8.9271*h = 0.65975
So h = 0.0739m or 7.39 cm
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