Question

1. An object is in circulation motion at a speed of 212 rad/sec when it begins to slow down at a constant rate of 2.7 radians per square second. How many rotations will the object make over the next 5.0 seconds? (Make sure your answer is the number of rotations.)

2. The total mass of the barbell is 2.8 kg. The distance between the man's elbow and hand is 43 cm. The distance between the man's elbow and shoulder is 43 cm. The angle between his forearm and the horizontal (labeled "1") is 34 degrees. The angle between his upper arm and the horizontal (labeled "2") is 15 degrees. Calculate the torque exerted by the barbell's weight about his elbow.

3. A certain front-loading washing machine has a drum of diameter 29.6 inches. A small tennis ball placed inside spins in a vertical circle pressed against the inner wall of the drum. How quickly would the drum have to spin (in radians per second) in order to ensure that the tennis ball remained pinned against the wall for the entire cycle without falling off?

Answer 1

1.

wo = initial angular velocity = 212 rad/s

t = time of travel = 5 sec

= Angular acceleration = - 2.7 rad/s2

= Angular displacement

Using the equation

= wo t + (0.5) t2

= (212) (5) + (0.5) (- 2.7) (5)2

= 1026.25 rad

n = number of rotations

Number of rotations is given as

n = /(2)

n = 1026.25 /(2(3.14))

n = 163.42