So far we’ve seen vectors showing direction of a force and distance and direction of motion. Motion is a change in where an object is.
Sometimes that motion is very slow. Other times the change is very fast. The measurement of how fast something moves is speed.
Notice speed concerns two things. One is distance as the object is moving from one place to another over a distance. The other is time. It measures how much distance an object goes in a certain amount of time.
Measuring distance requires a meter stick. Measuring time requires a stop watch.
Although it is possible to do Projects using a stop watch by yourself, having help makes them much easier.
Scientists use the metric system. If you don’t have a meter stick, you can use a yardstick. You can convert yards into meters by multiplying the yards by 0.914 meters per yard. For measurements in inches you multiply by 2.540 centimeters per inch.
Remember our Project about forces and friction when getting ready for this Project. You need a smooth floor without carpet this time to minimize friction. If you can’t find a place like that, put down smooth cardboard so the ball rolls over it at least a meter.
Question: Does mass affect speed?
2 balls of different weights
Ramp 1 meter long for the balls
Mass the balls and record the masses
Set up your ramp so the end is 0.5 m high where you will start the balls
Put the meter stick on the floor 10 cm away from where the ball will roll onto the floor but not so the ball will hit it
Mark where you will start the balls
Write down your prediction of whether speed is affected by mass or whether the light ball or heavy ball will be faster or if they will be the same.
You will start the stop watch when the ball gets to the meter stick and stop it when the ball gets to the end of the meter stick
Time how fast each ball covers the meter. Do each ball at least three times. Record the times.
Mass ball 1
Mass ball 2
Your prediction about the speed of the two balls:
Times for ball 1
Times for ball 2
Average the times for each ball by adding up all the times then dividing by the number of trials.
Compare the speeds of the heavy and light balls.
Do you think mass affects speed? Why do you think so?
What I Found Out:
The first thing I found out was that it is impossible to let a ball go down the ramp, back up to take a picture and time it for 1 meter at the same time. Luckily for me I found someone to help. Aiah Taylor was home from kindergarten for the day and was happy to let the ball go down the ramp whenever I asked.
My light ball had a mass of 3.00 g. the heavy ball had a mass of 18.00 g.
When we dropped the two balls, one heavy and one light, they fell at the same rate. I think their speed will be the same too.
The heavy ball had .44 sec for all three trials. That gave an average of .44 sec.
The light ball had .44 sec, .48 sec and .35 sec. That gave an average of .42 sec which was almost the same.
I found it was very difficult to time the ball for the 1 meter as it was going so fast.
Since the speeds were so similar, I don’t think mass affects speed.