# Forces and rotational motion

1. Nov 19, 2013

### ps3stephen

1. The problem statement, all variables and given/known data

This question is about forces and rotational motion.
(a) Figure 1.1 illustrates a force of 180 N acting at a perpendicular distance of 0.40 m from a point O. Calculate the torque about O.

(b) Figure 1.2 illustrates a circular drum of radius 0.080 m around which a rope is wound. The drum is turned by means of a handle of length 0.40 m to which a force of 180 N is applied at right angles to the handle.
Calculate the tension T in the rope.

(c) A person is pulling a boat on to a trailer using the drum system from (b), known as a winch, as shown in Figure 1.3. The person is exerting a force of 180 N on the handle.
Calculate the force which the trailer exerts on the axle of the winch when the handle is in the position shown in Figure 1.3.

2. Relevant equation
Torque=Force×distance

3. The attempt at a solution

(a) Torque=Fr=180(0.4)=72Nm
(b) ƩT=0
0.08T-180(0.4)=0
T=180(0.4)/0.08=900 Nm

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2. Nov 19, 2013

### haruspex

3. Nov 19, 2013

### ps3stephen

i am trying to figure out the free body diagram for part c