A wooden block with mass 1.50 kg is placed against a com- pressed spring at the

ID: 1371350 • Letter: A

Question

A wooden block with mass 1.50 kg is placed against a com-

pressed spring at the bottom of an incline of slope 30.0° (point A).

When the spring is released, it projects the block up the incline. At

point B, a distance of 6.00 m up the incline from A, the block is

moving up the incline at 7.00 m/s and is no longer in contact with

the spring. The coefficient of kinetic friction between the block

and the incline is uk = 0.50. The mass of the spring is negligible. k

Calculate the amount of potential energy that was initially stored in the spring.

total potential energy = work done against gravity + kinetic energy + work done aganst friction

work done against gravty U1 = mg sin(theta) x = 1.5x9.8 x 0.5 x 6 =44.1 J

kinetic energy U2 = 0.5 mv2 = 0.5 x 1.5 x 49 =36.75 J

work done against friction U3 = uk mg cos(theta) x = 0.5 x 1.5 x 9.8 x cos 30 x 6 = 38.19 J

total energy U =U1+U2+U3 = 44.1 +36.75 +38.19 =119.04 J

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