A 10-kg block on a horizontal frictionless surface is attached to a light spring
ID: 1311571 • Letter: A
Question
A 10-kg block on a horizontal frictionless surface is attached to a light spring (force constant = 1.2 kN/m). The block is initially at rest at its equilibrium position when a force (magnitude P) acting parallel to the surface is applied to the block, as shown. When the block is 8.0 cm from the equilibrium position, it has a speed of 0.80 m/s. How much work is done on the block by the force P as the block moves the 8.0 cm? A 2.5-kg object suspended from the ceiling by a string that has a length of 2.5 m is released from rest with the string 40° below the horizontal position. What is the tension in the string at the instant when the object passes through its lowest position?Explanation / Answer
a) total energy = total work done = 0.5 kx2+ 0.5 mv2 = 0.5 * 1200 * 0.082 + 0.5 *10* 0.82 =7.04 J = 7J
answer C
b)
h = 2.5*(1-cos50
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