EXPLORATION QUESTION:
How can we calculate the acceleration of a cart rolling down a ramp?
PURPOSE:
-Practice calculating acceleration with a set of data points.
-Create a Speed vs. Time graph.
BACKGROUND INFORMATION:
Imagine you’re sitting in a car at a stoplight. The light is red and so you aren’t moving. In a split second, the light switches from red to green. You take your foot and press hard on the gas pedal of the car. What happens? The car’s engine comes to life, the tires start to turn and you begin to move forward, quickly! You go faster and faster until you reach the speed limit and then you quit pressing the gas pedal…or accelerator.
That is the perfect example of when something accelerates. When something changes its speed, we say that it is accelerating. When something begins to go faster, it has a positive acceleration. When an object slows down, it has a negative acceleration. Whenever speed changes, acceleration is happening!
MATERIALS:
LabQuest2 computerPhoto-gates RampEnergy Car
SETTING UP THE LAB:
1. Set up the ramp as shown in the picture. Start the ramp out on the 2nd hole.
2.Place Photogate A in the position shown. Photogate B will start out 10 cm away from Photogate A.
DOING THE EXPERIMENT:
1.Keep Photogate A in the same place.
2. Set Photogate B 10 cm away from Photogate A down the track.
3.Place the cart at the top of the ramp.
4.Press “Play” on the LabQuest and let the cart roll down the ramp.
5.Collect data in the table below and make necessary calculations.
Distance from A to B(cm) / Unblocked Time through Photogate A
(s) / Time from Photogate A to Photogate B
(“Blocked B” subtracted by “Unblocked A”) / Time through Photogate B
(“Unblocked B” subtracted by “Blocked B”) / Speed through Photogate B
(cm/s)
10
20
40
50
60
70
How fast is the car moving as it goes through Photogate B? In order to calculate the speed, you will use the equation:
SPEED VS TIME GRAPH
1.Draw a graph with the speed (“Speed through Photogate B) on the y axis and the time it took to go that far (“Time from Ato B”) on the x-axis.
APPLYING WHAT YOU LEARNED:
1.Did the car accelerate as it traveled down the hill? How do you know? Explain.
______
______
______
2. Use the formula for acceleration to find the average acceleration of your car:
Show your work:
acceleration = ______
acceleration = ______cm/s/s
3.Use your Speed vs. Time graph to predict how much time it would take for the car to reach
a speed of 200 cm/s.
______
POSITION VS. TIME GRAPH FOR ACCELERATION
1.Use your data from the table to make a graph with the position (distance from A to B) on the y axis and the timeit took to go that far (time from A to B) on the x-axis.
2.Use your position vs. time graph to predict where on the track the car would reach aspeed of 200 cm/s.
______
3.Test your predictions with a photogate at your predicted location on the track. Were your predictions accurate? Have a teacher sign off to confirm: ______