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A 1.50 kg , horizontal, uniform tray is attached to a vertical ideal spring of f

ID: 1512816 • Letter: A

Question

A 1.50 kg , horizontal, uniform tray is attached to a vertical ideal spring of force constant 180 N/m and a 260 g metal ball is in the tray. The spring is below the tray, so it can oscillate up-and-down. The tray is then pushed down 15.2 cm below its equilibrium point (call this point A) and released from rest.

Problem 14.71 Part A How high above point A will the tray be when the metal ball leaves the tray? (Hint: This does not occur when the ball and tray reach their maximum speeds.) A 1.50 kg , horizontal, uniform tray is attached to a vertical ideal spring of force constant 180 N/m and a 260 g metal ball is in the tray. The spring is below the tray, so it can oscillate up-and-down. The tray is then pushed down 15.2 cm below its equilibrium point (call this point A) and released from rest. h= 24.8 cm Submit My Answers Give Up Correct Part B How much time elapses between releasing the system at point A and the ball leaving the tray? t= 0.223 Submit My Answers Give Up Correct Part C How fast is the ball moving just as it leaves the tray? 1 1 .98 u = m/s Submit My Answers Give Up

Explanation / Answer

Initial Energy stored in spring = 0.5*180*0.152 = 13.68 J
at h = 24.8 cm
PE gained = (1.5+0.26)*9.8*0.248 = 4.277 J
KE gained = 0.5(1.5+0.26)v^2 = 0.88v^2
By energy balance
0.88v^2 + 4.277 + 0.5*180*(0.248 - .152)^2 = 13.68
v = 3.121 m/s