Steven carefully places a 1.45-kg wooden block on a frictionless ramp, so that t

Question

Steven carefully places a 1.45-kg wooden block on a frictionless ramp, so that the block begins to down the ramp from rest. The ramp makes an angle of 56.3 degree up from the horizontal. Which forces non-zero work on the block as it slides down the ramp? How much total work has been done on the block after it slides down along the ramp a distance of Nancy measures the speed of the wooden block after it has gone the 1.81 m down the ramp. Predict speed she should measure. Now, Steven again places the wooden block back at the top of the ramp, but this time he jokingly gives the block a big push it slides down the ramp. If the block's initial speed is 2.00 m/s and the block slides down the ramp 1.81 m, what should Nancy measure for the speed of the block this time?

Explanation / Answer

1. gravity

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2. Work done by gravity W = mgh sin theta

W = 1.45 * 9.81 * 1.81 * sin 56.3

W = 21.41 Joules

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3. appply from the law of conservation of Energy

KE = PE

0.5 mv^2 = mgh

v^2 = 2* 21.41/(1.45)

V = 5.43 m/s

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4. appply change in KE = PE

0.5 m (Vf^2 - Vi^2) = 21.41

vf^2 - 2^2 = 2 * 21.41/(1.45)

Vf^2 = 29.53 + 4

Vf = 5.79 m/s

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