Wednesday, June 23, 2004

Centripetal Force 4 questions. plz help with ALL!! test prep =) i would really appreciate it.?

ive been trying these questions for a little while but i cant get the right answers. i would really appreciate it ifi could get help in understanding all 4 of these.please and thankyou =)

1)Jane whirls a rubber stopper tied to the end of a string in a horizontal circle of radius 1.25 m. If she whirls it 15 times in 7.85 s, what is the speed of the rubber stopper?


2)Janine has a mass of 27.5 kg. She is riding the merry-go-round at the playground. The surface of the merry-go-round is very slippery. The merry-go-round has an outside radius of 1.67 m and it rotates once every 1.93 s. How hard does she have to pull on the outside bars so as to keep from falling off?


3) piece of thread attaches an air puck to a spindle in the center of a horizontal air table. The puck is moving in a circular path of radius 1.38 m. The mass of the air puck is 28.8 g and the thread can withstand 3.50 N of force. What is the maxiumum speed the puck can go without breaking the thread?


4)A 1.35 kg pendulum bob swings in a vertical circle with a radius of 1.44 m. The speed of the pendulum at the lowest point in the swing is 1.64 m/s. What is the tension in the string at this point?

Answer on Centripetal Force 4 questions. plz help with ALL!! test prep =) i would really appreciate it.?

Angular frequency ? = 2? N where N is the cycles /second.

? = v/r where v is the linear velocity and r is the radius of the circle.

Centripetal acceleration = v^2/r or r?^2

Centripetal force = m v^2/r or m r?^2
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1
v= r ? = 2? r N = 2? *1.25*(15/7.85) = 15.01 m/s

2.
F = m r?^2 = 27.5 *1.67 (2? N) ^2 = 27.5 *1.67 (2? 1/ 1.93) ^2 = 486.74 N

3.
F = m v^2/r
3.5 = 0.0288* v^2/ 1.38
v^2 = 167.71
v = 12.95m/s

4.
Tension T = (mv^2/r + mg) = 1.35*1.64^2/1.44 + 1.35*9.8 = 15.75 N
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