A 0.2 kg rocket that was launched is moving at 60 m/s when it ignites its boosters and 425 J of work was done by the force generated burning of the propellant in its boosters. Find the speed of the rockets after is has moved up 29 m from its ignition.
Solution :
Given :
mass (m) = 0.2 kg
initial velocity (u) = 60 m/s
Work done by force generated burning of the propellant in its boosters (WP) = 425 J
Height (h) = 29 m
According to Work-Energy principle : Change in Kinetic energy = Net Work done.
KEfinal - KEinitial = WP - Wgravity
(1/2) m v2 - (1/2) m u2 = WP - m g h
(0.5)(0.2 kg) v2 - (0.5)(0.2 kg)(60 m/s)2 = (425 J) - (0.2 kg)(9.81 m/s2)(29 m)
(0.1) v2 - 360 = 368.102
v2 = 7281.02
v = 85.33 m/s
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