27
012-07558A
PAScar Accessory Track Set (2.2 Meter)
®
Experiment 8: Newton’s Second Law II
EQUIPMENT NEEDED:
– PAScar (ME-6950)
– Dynamics Track
– Super Pulley with clamp (ME-9448A)*
– Base and support rod (ME-9355)*
– String*
– Mass hanger and mass set (ME-9348)*
– Stopwatch (SE-8702B)*
– Wooden or metal stopping block*
– Mass balance (SE-8723)*
(See Procedure Step 3.)
Purpose
The purpose is to verify Newton’s Second Law,
F = ma
.
Theory
According to Newton’s Second Law,
F = ma
.
F
is the net force acting on the object of
mass
m
and
a
is the resulting acceleration of the object.
For a car of mass
m
1
on a horizontal track with a string attached over a pulley to a mass
m
2
(see Figure 7.1), the net force
F
on the entire system (car and hanging mass) is the
weight of hanging mass,
F = m
2
g
, assuming that friction is negligible.
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
. This experiment will
check to see if
m
1
g
is equal to
(m
1
+ m
2
)a
when friction is ignored.
To obtain the acceleration, the car will be started from rest and the time (
t
) it takes for it to
travel a certain distance (
d
) will be measured. Then since
d
= (1/2)at
2
, the acceleration
can be calculated using
(assuming a = constant)
Procedure
1. Level the track by setting the car on the track to see which way it rolls. Adjust the level-
ing 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 and record in Table 8.1.
3. Attach the pulley to the end of the track as shown in Figure 8.1. Place the dynamics car
on the track and attach a string to the hole in the end of the car and tie a mass hanger on
the other end of the string. The string must be just long enough so the car hits the stop-
ping block before the mass hanger
reaches the floor.
4. Pull the car back until the mass hanger
reaches the pulley. Record this posi-
tion at the top of Table 8.1. This will
be the release position for all the trials.
Make a test run to determine how
much mass is required on the mass
Figure 8.1 Equipment Setup
adjustable
end stop
*Not included in Track Set
a
= 2
d
t
2
Summary of Contents for ME-6956
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