1) A pendulum of length 50 cm is pulled 30 cm away from vertical axis and releas
ID: 1703082 • Letter: 1
Question
1) A pendulum of length 50 cm is pulled 30 cm away from vertical axis and released from rest. What is its speed at bottom of of its swing?2) A projectile of mass m leaves ground with kinetic energy of 220 J At highest point in its trajectory its KE is 120J. To that vertical height relative to its launch point did it rise?
3) A rifle bullet is fired at angle of 30 degrees below horizontal with initial velocity of 800m/s from top of cliff 80 m high. How far from base of cliff does it strike the level ground below?
Explanation / Answer
conservation of energy. 1) mg*(-0.5)+mv^2/2=mg*(-0.4). so v^2/2=g*0.1 so v=1.4(m/s). 2) ?Q=mgh so 220-120=mgh so h=100/mg 3) time for it to reach the ground. 800*sin30*t+gt^2/2=80. so t=161(s). so D=800*cos30*161=1.11e5(m)
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