1) To throw the discus, the thrower holds it with a fully outstretched arm. Star

Question

1) To throw the discus, the thrower holds it with a fully outstretched arm. Starting from rest, he begins to turn with a constant angular acceleration, releasing the discus after making one complete revolution. The diameter of the circle in which the discus moves is about 1.7m. If the thrower takes 1.2s to complete one revolution, starting from rest, what will be the speed of the discus at release?

2) The tune-up specifications of a car call for the spark plugs to be tightened to a torque of 44N?m . You plan to tighten the plugs by pulling on the end of a 30-cm-long wrench. Because of the cramped space under the hood, you'll need to pull at an angle of 120? with respect to the wrench shaft. With What force must you pull?

Explanation / Answer

1.

1 rev = 6.283 radians

6.283/(1.2sec/2) = (u + v) = 10.47

u = 0

v = 10.47 rad/s

tangential velocity = rad/s x radius

radius = 1.7/2 = 0.85 m

10.47 x 0.85 =8.90m/s

2.If F is the force, then F sin 60 is the amount perpendicular to the lever.
You need 44 Nm and that has to equal (Fsin60)(0.3)
(Fsin60)(0.3) =44
0.259F = 44
F = 169.35Newtons

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