#4 Ball Speed

EXPERIMENT:

Find two balls of different sizes and weight (tennis ball, soccer ball, basketball, etc). Roll each ball down an incline (a slide at a playground would work). Note length of incline. Time how long it takes for each ball to get down. Take a third ball of different size and weight and make a prediction about how long it will take to get down. 

PREDICTION:

The heavier ball will get down the ramp faster.

OBSERVATION AND DATA:

I used a tennis ball, a size 5 soccer ball, and a plastic playing ball in this experiment.  At first I timed the balls rolling down the 8ft incline with a stop watch.  My results were all over the place.  Please see table below:

I accounted this to human error.  I then decided to race the balls.  I did two balls at a time.  The tennis ball beat both balls down the ramp each time.  The pink ball beat the the soccer ball down the ramp.

CONCLUSION:

Given the shortness of the inclined track (8 ft) and the fact that I timed these using my eyes and a wristwatch stopwatch, human error has really creeped into these results. It's hard to discern what the fastest ball was, however, the tennis ball "seemed" to be the fastest followed by the pink smooth ball. The soccer ball was last.

Human error and lousy time keeping aside, there are three main factors going into what ball reaches the bottom of the incline first.

1. Friction between the surface of the ball and the surface of the plywood.
2. Air resistance against the different balls.
3. Mass of each ball.

The balls are going to roll down the incline at the same rate regardless of their mass because with only 8 ft. to go, they never reach terminal velocity. The air resistance is negligible with such a short run. The friction was different between the three varying ball types. So, even though the times are all over the place, one can generally see that the tennis ball was the fastest followed by the pink ball. The soccer ball brought up the rear.