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# Launching a block up a ramp - 3

last edited by 4 years, 3 months ago

6.3.P8b

The apparatus shown in the figure below uses a spring to launch a small block along a track. A latch holds the block of mass m in place against the compressed spring (spring constant k) as shown. When the ring is raised the block is launched along the track.  The part from B to C has significant friction (coefficient of sliding friction, µ). When it reaches D it slides up the ramp to point E. The parts of the track from A to B and from C to E can be considered frictionless for this problem and the size of the mass can be ignored compared to the distances along the ramp.

When the block is launched, it gets through the frictional part, rises up the ramp to the point D, a height h above the straight part of the ramp. It then slides back down. On its return, it gets to the point B and stops. The distances are shown on the figure and the angle of the ramp is θ as shown.

Given the following values for the parameters, can you calculate the value of the coefficient of friction, μ ? If you can, do so and explain how you did it. If not, explain why not and what information would allow you to calculate it.

• m = 75 g
• k = 15 N/m
• d1 = 10 cm
• d2 = 10 cm
• d2 = 10 cm
• d3 = 8 cm
• L = 25 cm
• θ = 20o

If you need the earth's gravitational field, use the approximate value g = 10 N/kg.

Joe Redish 3/30/15