problem18. Suppose the pendulum passes by something as it swings, not right at t

Question

problem18.

Suppose the pendulum passes by something as it swings, not right at the extreme points. If we ask how often the pendulum swings by object what would the correct answer be

a. f

b .2f

c. w

d.2w

problem 19

For the rest of the problem involving pendulum, m=20kg and l=20m. suppose the pendulum is at the top, moving at 12m/s horizontally. How fast will it go at the bottom

a. 13m/s

b. 23m/s

c. 31m/s

d. 52m/s

e. We can’t tell. The ball isn’t moving fast enough at the top for a cable of tension to exist,and just fall freely

Problem 20

Suppose instead, the pendulum is moving 16m/s horizontally at the top. How fast will it go at the bottom?

a. 17m/s

b. 26m/s

c. 32m/s

d. 56m/s

e. We can’t tell. The ball isn’t moving fast enough at the top for a cable of tension to exist, and just fall freely(like a free-falling body) until it’s yanked by cable somewhere near bottom

Problem 21

For this rest of the problems with this pendulum, assuming small oscillations. What is the period of the pendulum?

a. 1s

b. 4.9s

c. 8.9s

d. 17.7w

e. We can’t tell without knowing amplitude of oscillation

Problem 22

Suppose at time t=0, the pendulum is =3 and moving at 1.0m/s. what is the intial angular speed?

a. 0.05/s

b. 0.71/s

c. 2.9/s

d. 12/s

e. 41/s

Problem 23

The equation describing the oscillation of the pendulum with the previous problem’s initial condition is (t)=Acos(wt)+Bsin(wt) What are A and B ?

a. A= 3, B=0.05/s

b. A=3, B=0.71/s

c. B=3, A= 2.9/s

d. B=3 A=12/s

e. A= 5, B= 41/s

problem 24

What is amplitude (m) ( is up like a power)

a. m =A+B

b. m =|A-B|

c. m =A

d. m = sqrtA2+B2

e. m sqrt A2-B2

Explanation / Answer

a) f is frequency of pendulum (no of time it passes by the point)

Ans(a)

19) using energy conservation,

PE + KE = constant

m * g * 20 + m * 12^2 /2 = 0 + m v^2 / 2

v = 23.15 m/s

Ans(b)

20) m * g * 20 + m * 16^2 /2 = 0 + m v^2 / 2

v = 25.5 m/s

Ans(b)

21) T = 2pi sqrt(l/g)

   = 2 pi sqrt(20/9.8) = 8.9 sec

Ans(C)

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