NSC 101 Laboratory for 2/3/98

Introduction

There are two forms of energy important to this lab:

1. Kinetic Energy (KE), the energy associated with motion and
2. Gravitational Potential Energy (PE), the energy associated with height.

If forces such as friction and air resistance can be ignored, then as an object rolls or slips down an incline, its gravitation PE decreases (as height decreases) and its KE increases (as velocity increases) by the same amount. We will test this simple idea in this week's lab.

Rather than a small experiment inside the lab, we are thinking big and heading outside this week. We have a bicycle (a dirt bike) and a hill. A volunteer rider will coast down the hill near the CA Building on the bike. You are going to measure the speed of the bike and rider at the bottom of the hill and you are going to measure the vertical height of the hill. Using this data, you will test to see if the PE at the top of the hill is equal to the KE at the bottom of the hill.

Equipment:

A bicycle, some stop watches, a couple traffic cones, a 200 ft tape measure, and a hill.

Meter sticks, carpenters levels, masking tape, straws, and anything else available in the lab that you wish to use.

BE SURE to dress appropriately for a few hours of outside activity.

The Experiment:

The hill we will use is on the main road in front of the CA building parking lot. The volunteer cyclist will start at the first speed bump as you move up the hill. This is just above the lower pedestrian crosswalk. The bottom of the hill is roughly where the road levels off, near where the older concrete ends and the newer asphalt begins.

You must devise a method to:

1. measure the speed of the cylist and bike at the "bottom" of the hill, and
2. measure the vertical height of the hill.

The first task of measuring speed should be straight foward, but spend some time thinking about the problem. There is more than one good method and the logistics need to be figured before starting.

The second task, measuring the height of the hill, is a bit more challenging. Examine the hill and surrounding area in the next few days and start thinking about a method for accomplishing this task. You do not have to know trigonometry to do this! Consider using levels and line of sight methods.

Safety We will block off the northern-most lane with yellow sawhorses and traffic cones. However, everyone must constantly watch for cars, especially cars leaving the parking lot near the bottom of the hill. There will be plenty of time to do the experiment, so extra caution will be in order.