PASCO ME-6955 1.2 m PAScar Dynamics System - Manual (Page 20)

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1 . 2 m P A S c a r D y n a m i c s S y s t e m E x p e r i m e n t 7 : N e w t o n ’ s S e c o n d L a w
20
Experiment 7: Newton’s Second Law
Purpose
In this experiment, you will verify
Newton’s Second Law, F = ma.
Theory
According to Newton’s Second Law, F = ma, where F is the net force acting on the
object of mass m, and a is the resulting acceleration of the object.
For a cart of mass m
1
on a horizontal track with a string attached over a pulley to a
hanging mass m
2
(see Figure 7.1), the net force F on the entire system (cart and hang-
ing mass) is the weight of hanging mass, F = m
2
g, (assuming that friction is negligi-
ble).
According to Newton’s Second Law, this net force should be equal to ma, where m is
the total mass that is being accelerated, which in this case is m
1
+ m
2
. You will check
to see if m
1
g = (m
1
+ m
2
)a as predicted by theory.
To determine the acceleration, you will release the cart from rest and measure the time
(t) for it to travel a certain distance (d). Since d = (1/2)at
2
, the acceleration can be cal-
culated using .
Procedure
1. Install the feet on the track and level it.
2. Install the end stop on the track near one end with the magnets facing away from
the track.
3. Measure the mass of the cart and record it in Table 7.1.
4. Attach the pulley and end stop to the track as shown in Figure 7.1. Place the cart
on the track. Tie a string to the lower attachment point of the cart. Tie a mass
hanger on the other end of the string. Run the string under the end stop and over
the pulley. Adjust the pulley so that the string runs parallel to the track. The string
must be just long enough so the cart reaches the end stop before the mass hanger
reaches the floor.
Required Equipment from Dynamics System
Track with Feet and End Stop
PAScar
Cart Mass
Other Required Equipment Suggested Model Number
Super Pulley with Clamp ME-9448A
Stopwatch ME-1234
Mass hanger and mass set ME-9348
Mass balance SE-8723
String (about 2 m)
Figure 7.1
a 2d t
2 
=