Background:

Newton's first law states that acceleration can only occur if a net force is applied to an object. While it is easy to tell whether an object is moving or not, it is not always easy to see if acceleration is taking place.

With the help of a special sensor, acceleration is easy to detect. In this lab, you will use a visual accelerometer to observe the changes in motion of a cart as force is applied. As a preview to your studies of Newton's Laws, the mass of the cart will be changed to determine the effect on acceleration when a net force is applied.

The Question:

Is acceleration evident when force is applied to an object? How does acceleration change when the mass of the object is changed?

Variables:

This experiment involves these variables: cart mass, net force on the cart, cart acceleration. Identify and state the manipulated, responding, and controlled variables in this investigation.

Materials:

Procedure:

Step 1:

Plug the accelerometer into the USB link that has already been connected to the computer:

Note that the accelerometer has an adjustable scale:

The appropriate settings are "manual scale", using the 20 m/s² setting, although you may wish to experiment with a lower setting depending on the strength of your cart launcher. The lights on the accelerometer will illuminate according to the amount of positive or negative horizontal acceleration. Each light on the display represents a one-fifth division of the red or green scale.

The black button in the centre of the two scales is used to turn on the accelerometer and zero the scale.

Configure the DataStudio software to display an acceleration versus time graph.

Step 2:

Attach the accelerometer to the dynamics cart. Attach the cart launcher to the end of the dynamics track. Place the accelerometer and dynamics cart up against the cart launcher.

Step 3:

Load the cart launcher to a small setting so that it will release with a small amount of force. Click "Start" in the DataStudio software to begin collecting data, and watch the time scale carefully. As close to the 5 second mark as possible, release the cart launcher to propel the cart down the track. When the cart is launched, note what happens on the visual scale of the accelerometer. As soon as the cart has been propelled, stop data collection.

Step 4:

Repeat step 3, but first adjust the cart launcher to a slightly higher setting so that it will propel the cart with a greater force. Repeat step 3 several times, each time increasing the amount of force that the cart launcher delivers.

When you have completed several repeats of step 3, scale your graph and print it out. This will be referred to later as "graph 1". Clear the data that you have collected so far.

Step 5:

As in step 3, load the cart launcher to a small setting so that it will release with a small amount of force. Click "Start" in the DataStudio software to begin collecting data, and watch the time scale carefully. As close to the 5 second mark as possible, release the cart launcher to propel the cart down the track. When the cart is launched, note what happens on the visual scale of the accelerometer. As soon as the cart has been propelled, stop data collection.

Step 6:

Repeat step 5, but first add a 250-g mass to the top of the acceleration sensor and cart. Repeat step 5 again, once more increasing the amount of mass on the acceleration sensor and cart.

When you completed 2 repeats of step 5 (each time with more mass), scale your graph and print it out. This will be referred to later as "graph 2".

Analyzing and Interpreting:

1.	Carefully note and circle the peaks on graph 1. With the help of the acceleration scale and a ruler, determine the acceleration values for each of the peaks (alternatively, this can be done using the "smart cursor" feature of the DataStudio software).
2.	Carefully note and circle the peaks on graph 2. With the help of the acceleration scale and a ruler, determine the acceleration values for each of the peaks (alternatively, this can be done using the "smart cursor" feature of the DataStudio software).

Forming Conclusions:

3.	Describe how the lights on the acceleration sensor illuminated when you launched the cart. What did this indicate concerning the application of force on an object?
4.	Consider your graph 1 results. How did acceleration change as the force on the dynamics cart was increased?
5.	Consider your graph 2 results. How did acceleration change as the mass of the dynamics cart was increased?
6.	Discuss the proportionality of force, mass and acceleration.

Applying and Connecting:

Explain the reason for each of the situations below using what you have learned from this lab.

7.	Racing vehicles such as Formula One cars are designed to have as little mass as possible.
8.	"Reverse Bungees" are exciting carnival rides where the riders are pulled downward to make the bungee cords tight, then the cords are released to fling the riders into the air. The tighter the bungee cords are pulled, the more exciting the ride.

Extending:

9.

Force is measured in newtons. In this lab, the specific number of newtons delivered by the cart launcher was not recorded. Repeat this experiment by first calibrating the force sensor so that the number of newtons per launch is known. When you have finished collecting your graph data, use the force of the launcher and the peak acceleration values to create an acceleration versus force graph. Discuss your findings.