# Force of bicyclist physics problem

1. Oct 19, 2006

### spoonthrower

A bicyclist is coasting straight down a hill at a constant speed. The mass of the rider and bicycle is 60.0 kg, and the hill is inclined at 19.0° with respect to the horizontal. Air resistance opposes the motion of the cyclist. Later, the bicyclist climbs the same hill at the same constant speed. How much force (directed parallel to the hill) must be applied to the bicycle in order for the bicyclist to climb the hill?

I am so lost with this one and have no idea where to start.

2. Oct 19, 2006

### gunblaze

Note this:"climbs the hill at the same constant speed" What does this imply about the cyclist when he was coming down the hill? What can you find from this?

When he is going up the hill, again wat are the forces that apply on him? Compare the 2 situations, one when the cyclist is coming down the hill and the other, when the cyclist is moving up the hill. Draw out a free body diagram for both cases and see the differences in forces acting on the cyclist.

3. Oct 20, 2006

### spoonthrower

I know constant speed means there is no acceleration....but I dont see how i can solve anything for this.......and does air resistance play a part when he climbs up the hill???? help?

4. Oct 22, 2006

### gunblaze

Yes. there is air resistance but the fact that the cyclist is moving at constant speed tells us more than just that he is not accelerating. It also tells us that the cyclist have no resultant force down the slope right?