PASCO ME-6950 PAScar with Mass - Manual (Page 8)

012-07361B PAScar with Mass
7
Purpose
In this lab, a small mass m will be connected to the PAScar by a string as shown in Figure
3.1. The string will pass over a pulley at the table’s edge so that as the mass falls the car
will be accelerated over the table’s surface. As long as the string is not too elastic and
there is no slack in it, both the falling mass and the PAScar will have the same accelera-
tion. The resulting acceleration of this system will be experimentally determined and this
value will be compared to the acceleration predicted by Newton’s Second Law.
Theory
The car will be released from rest and allowed to accelerate over a distance d. Using a
stopwatch, you will determine how long it takes, on average, for the car to move through
the distance d. An experimental value for the car’s acceleration a can be determined
from:
Assuming that the tabletop is truly horizontal (i.e. level), Newton’s Second Law ( F = ma)
predicts that the acceleration of this system will be:
Procedure
1. Set up the pulley, car, and a bumper of some sort to prevent the car from hitting the
pulley at the end of its run. Add the following masses to the bed of the car: 10 g, 50 g,
500 g and two 20-gram masses.
2. Carefully level the table until the car has no particular tendency to drift or accelerate in
either direction along its run.
3. Put a loop in one end of the string and place this loop over the spring-release trigger on
the PAScar. Drape the string over the pulley. Adjust the pulley so the string is level.
4. Adjust the length of the string so that the longest arrangement of masses that you intend
to use will not hit the floor before the car has reached the end of its run. Put a loop in this
end of the string.
Experiment 3: Newton's Second Law
(Predicting Accelerations)
Figure 3.1
EQUIPMENT NEEDED:
– PAScar (ME-6950)
– Pulley and pulley clamp (ME-9448)
– Mass set (SE-8704)
– Stopwatch (SE-8702)
– String
– Paper clips
– Block (to act as bumper)
– Balance (SE-8723 or equiv.)
d = at 2 which leads to: a = (Experimental Value) 2 d
Trigger
Paper clips
a = or
F
net
M
TOTAL
m
M
TOTAL
Bumper
block
1
2 t 2
a = ( ) g (Theoretical Value)