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Question

The mass of a simple pendulum of length, L = 1.0 m is released with the string originially in a horizontal position.. (a) Calculate the speed of the mass at its lowest position. (b) what is the speed when the string makes an angle of 45 degrees with the vertical? (c) Determine the tension in the string in both poistions if the mass is .2 kg

andddd

A machine gun in automatic moe fires 20-g bullets with v(bullet) = 300 m/s at 60 bullets/s. (a) if the bullets enter a thick wooden wall, whts is the average force exerted against the wall? (b) if the bullets hit a steel walland rebound elastically, what is the average force on the wall?

Answer 1

1. Pendulum.

T=2pi sqrt(L/g) but who cares

a) Pe=Ke
mgh=0.5mV^2 or
V= sqrt(2gh) where h=L
V=sqrt(2gL)

b) V=sqrt(2gL(1-cos(45))

c) Horizontal position T=0
at 45 degrees and is the mass is not moving
T=mgcos(45) if it is in motion we have to add centripetal component.