# Calculating the speed of an object going down an incline

1. Oct 11, 2007

### lull

Hello, all. How do I find the speed of something going down a ramp if I know the total weight of the object (214 pounds) the angle of the ramp (15 degrees) the frictional coefficient (.0236) the ramp is 11 feet long.

2. Oct 11, 2007

### Staff: Mentor

Draw a free body diagram of the object (it's sliding and not rolling, right?, and it is released from rest at the top of the ramp?), showing the forces acting on it (gravity, friction) as vectors, then figure out what motion occurs.

If the coefficient of static friction is high enough, the object will not start sliding. If it isn't high enough, the object will have a net constant acceleration down the ramp. Once you use the FBD to figure out the net force down the ramp, use the object's mass to calculate the net constant acceleration, and use that in the kinematic equations of motion to calculate the velocity versus time for the block.

3. Oct 11, 2007

### lull

It is a person on a bicycle going down a ramp. And yes, they are at rest in the beginning.

4. Oct 11, 2007

### lull

Also, is it possible if anyone can provide a few formulas? This is for a project but we weren't given any formulas and only given all the information today and it's due tommorow >.<! Thank you all sooo much

5. Oct 11, 2007

### Staff: Mentor

Here is a link to the kinematic equations of motion for constant acceleration (like due to gravity):

http://en.wikipedia.org/wiki/Kinematic_equations#Equations_of_uniformly_accelerated_motion

You will need to neglect the mass of the bicycle tires (probably reasonable), so that it is all linear momentum that builds as the bike accelerates down the incline (and no rotational momentum imparted to the tires).