PASCO PS-2141 Force Platform - Manual (Page 8)

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F o r c e P l a t f o r m E x p e r i m e n t : B o u n c i n g B a l l
8
Sample Data and Teachers’ Notes
Part 1
The ball is allowed to bounce three times. Before the second
bounce, the hang time is 0.832 s.
After the second bounce, the hang time is 0.730 s.
The weight of the ball is 5.74 N; thus m
= 0.585 kg, and
For the second bounce, the impulse determined from area under the force versus time
plot is 4.54 N·s, about 1% deviation from
∆P calculated above.
The area under the curve is an approximate measure of impulse, since the graph shows only the
force exerted by the platform, not the net force on the ball (which includes gravitational force). A
more correct measure of impulse can be obtained by taring the platform with the ball resting on it
so that the measured force equals the net force on the ball; however this would make little practi-
cal difference.
Part 2
In this case, the maximum force is about 40 times the weight
of the ball (results will vary with the type of ball and its initial
height). The measured force is zero when the ball is in the air.
The maximum force of the bounces decays exponentially.
After the balls stops bouncing, the ball oscillates on the plat-
form. At first, the minimum force goes almost down to zero,
indicating that the ball is almost bouncing off the platform. As
the amplitude decreases, the minimum of each cycle
approaches the static weight of the ball.
When the ball has come to rest, the measured force is its
weight, equal to mg.
V
down
1
2
---gt
before
–
1
2
--- 9.81 m/s
2 ( ) 0.832 s ( )
– 4.08 – m/s = = =
V
up
1
2
---gt
after
1
2
--- 9.81 m/s
2
( ) 0.730 s ( ) 3.58 m/s = = =
∆P
m V
up
V
down
–
( )
=
0.585 kg
( ) 3.58 m/s 4.08 m/s
+
( ) 4.48 N·s
= =