1)Find the angular speed of a CD must have to give a linear speed of 1.25m/s at
ID: 1288250 • Letter: 1
Question
1)Find the angular speed of a CD must have to give a linear speed of 1.25m/s at the point the laser beem shines on the disk when it is 2.5cm from it's center.
2)a game show has contestants spin a wheel when it is their turn. One contestant gives the wheel an initial angular speed of 3.40 rad/s. It then rotates through one-and-one-quarter revolutions and comes to rest on the BANKRUPT space. Find the angular acceleration of the whee, assuming it to be constant (in rad/s^2).
3)How many seconds does it take for the wheel in question 2 to come to rest?
4)The lunar rover had a mass of 225 kg. What was its weight in Newtons on the Moon? (Mass of the moon is 7.35x10^22kg and its radius is 1.74 x 10^6)
Explanation / Answer
linear speed v = 1.25 m/s
raduis , r = 2.5 cm = 0.025 m
angular speed , w = v/r = 1.25/0.025 = 50 rad/s
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2)
from the relation
w2-^2 -w1^2 = 2aS
S = 1.25 rev = 1.25*2pi rad = 7.85 rad
so
0^2 - 3.40^2 = 2a(7.85)
angular acceleration
a = - 0.736 rad/s^2
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3)
from
w2 = w1 + at
0 = 3.40 +(-0.736) t
time , t = 4.617 sec
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4)
weight = mg = m.GM/r^2 = 225*6.67x10^-11*7.35x10^22/(1.74x10^6)^2 = 364.33 N
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