A 1.7 kg breadbox on a frictionless incline of angle = 43 is connected, by a cor
ID: 1423248 • Letter: A
Question
A 1.7 kg breadbox on a frictionless incline of angle = 43 is connected, by a cord that runs over a pulley, to a light spring of spring constant k = 120 N/m, as shown in the figure. The box is released from rest when the spring is unstretched. Assume that the pulley is massless and frictionless. (a) What is the speed of the box when it has moved 10.8 cm down the incline? (b) How far down the incline from its point of release does the box slide before momentarily stopping, and what are the (c) magnitude and (d) direction of the box's acceleration at the instant the box momentarily stops?
I know that the answers to (a) is .81m/s and (b) is .18m, but I have no idea how to answer (c) and (d).
Explanation / Answer
(c) .The force of the spring is: F = k*d , parallel to the slope. The component of force due to gravity, parallel to the slope is: m*g*Sin(). The net force is:
F = k*d - m*g*Sin()
a = F/m = k*d/m - g*Sin() = 120*.18/1.7 - 9.8*Sin(43) = 6.022 m/sec^2
d.
parallel to the incline surface, and up.
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