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1. A 8.00-kg object is hung from the bottom end of a vertical spring fastened to

ID: 1373253 • Letter: 1

Question

1. A 8.00-kg object is hung from the bottom end of a vertical spring fastened to an overhead beam. The object is set into vertical oscillations having a period of 1.80 s. Find the force constant of the spring.

2. A 0.72-kg block attached to a spring with force constant 152 N/m is free to move on a frictionless, horizontal surface as in the figure below. The block is released from rest after the spring is stretched 0.13 m.

a. At that instant, find the force on the block: magnitude (unit:N)and direction

b. At that instant, find its acceleration: magnitude (unit: m/s^2) and direction

Explanation / Answer

(1)

force constant is

k = w^2 m = ( 2pi/T)^2 m = (2 pi/ 1.80 s)^2 8 kg = 97.37 N/m

(2)

force on the block is

F = kx = ( 152 N/m) ( 0.13 m) = 19.76 N ( forward direction)

from the newton second law accleration of the block is

a = F/m = 19.76 N/ 0.72 kg = 27.44 m/s^2

opposite to the direction of the force ( revese direction)