Pasco Scientific ME-6956, Инструкция по эксплуатации и руководство по экспериментам, Страница: 33 / 46

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012-07558A PAScar Accessory Track Set (2.2 Meter)
®
Experiment 9: Conservation of Energy
EQUIPMENT NEEDED:
– PAScar with Mass (ME-6950) – Dynamics Track
– Super Pulley with Clamp (ME-9448A)* – Meter stick*
– Base and support rod (ME-9355)* – Mass hanger and mass set (SE-8759)*
– String* (several kilograms)
– Mass balance (SE-8723)* – Graph paper*
Purpose
The purpose is to examine spring potential energy and gravitational potential energy and
to show how energy is conserved.
Theory
The potential energy of a spring compressed a distance x from equilibrium is given by
PE = (1/2)kx 2 , where k is the spring constant. According to Hooke’s Law, the force
exerted by the spring is proportional to the distance the spring is compressed or
stretched,
F = kx
, where
k
is the proportionality constant. Thus, the spring constant can
be experimentally determined by applying different forces to stretch or compress the
spring different distances. When you plot the force versus the distance, the slope of the
resulting straight line is equal to
k
.
The gravitational potential energy gained by a car as it climbs an incline is given by
potential energy = mgh , where m is the mass of the car, g is the acceleration due to
gravity, and
h
is the vertical height the car is raised. In terms of the distance,
d
, along the
incline, the height is given by
h =d sin
θθθθθ
.
If energy is conserved, the potential energy in the compressed spring will be completely
converted into gravitational potential energy.
Determining the Spring Constant
Procedure
1. Level the track by setting the car on the track to see which way it rolls. Adjust the
leveling feet to raise or lower the ends until the car placed at rest on the track will not
move.
2. Use the balance to find the mass of the car. Record this value in Table 9.2.
3. Set the car on the track with the spring plunger against the stopping block as shown in
Figure 9.1. Attach a string to the car and attach the other end to a mass hanger, passing
the string over the pulley.
4. Record the car’s position in Table 9.1.
5. Add mass to the mass hanger and record the new position. Repeat this for a total of 5
different masses.
*Not included in Track Set