s as polnts) An ideal pendulum consists of a massless rigid rod of length R-2m a
ID: 1789586 • Letter: S
Question
s as polnts) An ideal pendulum consists of a massless rigid rod of length R-2m and a particle ass m-i kg at its end. The pendulum is initially at rest at its highest point (point A) (5 points) Calculate the gravitational potential energy of the pendulum at point A relative to point B. a. b. (5 points) The pendulum is now released from rest from point A and makes a half-swing to its lowest pendulum at point B. point (point B). Calculate the kinetic energy of the c. (5 points) What is the velocity of the pendulum at point B? d. (5 points) Find the force exerted on the particle by the rod at point B. e. (5 points) How will the answer in part (d) change if the length of the rod is increased by a factor of 4?Explanation / Answer
a.
PEi=mg*h=mg*2R = 2mgR=2*1.0*9.8*2= 39.2 J -------(1)
b.
By law of conservation of energy,
KEf= PEi--------(2)
Plugging (1) in (2),
KEf=39.2 J
c.
KEf=1/2mvf^2
39.2=1/2*1.0*vf^2
vf= 8.85 m/s
d.
Fnet = Fc
Fnet = mvf^2/R = (1.0*8.85^2)/2.0 = 39.12 N
e.
Let us first find vf,
1/2mvf^2=mg*h = mg*(4*R) =
½*1.0*vf^2=1.0*9.8*4*2
vf=12.5 m/s
Fnet = mvf^2/R = (1.0*12.5^2)/2.0 = 78.12 N
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