# Fan Cart Physics Gizmo Answer Key

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You may be looking for Fan Cart Physics Gizmo Answer Key. If yes, you are able to check the answer key below according to the Scribd that was uploaded by JoonSmith and it can be accessed at here. However, before you check the answer key, it is important for you to note that the answer key can only be used for learning and not for cheating.

Prior Knowledge Questions (Do these BEFORE using the Gizmo)

1. Imagine a horse pulling a cart. What would happen to the speed of the cart if several bags of cement were added to the cart?

Answer: It would slow down, as the greater the mass the more force it takes to move/ accelerate.

1. Suppose several more horses were hitched up to the same cart. How would this affect the speed of the cart?

Although these questions may seem simple, they form the basis of Newton’s second law of motion. The Fan Cart Physics Gizmo can be used to illustrate all three of Newton’s laws.

Gizmo Warm-up

The Fan Cart Physics Gizmo shows a common teaching tool called a fan cart. Place fan A

on the cart and turn it on by clicking the ON/OFF button below.

1. Look at the blue lines coming from the fan. In which direction is the air pushed?

1. Press Play and observe the cart. In which direction does the cart move?

By blowing to the left, the fans exert a force on the cart that pushes it to the right. This illustrates Newton’s third law: A force in one direction results in an equal force in the opposite direction.

1. The velocity (v) of the cart is its speed and direction. Click Reset. Select the BAR CHART tab, and click Play. Does the velocity change or stay the same?

A change in velocity is called acceleration (a).

Question: What happens to the cart when there is no force?

1. Form hypothesis: What will the motion of the cart be like when there is no force at all?

Answer: (There is no friction in this model.) It will stay still.

1. Predict: Suppose a cart with no fans has a starting velocity of 2 m/s. What will be the velocity of the cart when it reaches the wall?

1. Experiment: Check that there are no fans on the cart. On the DESCRIPTION tab, set the

Initial velocity of cart to 2.0 m/s. Select the BAR CHART tab, and click Play. What do you notice about the velocity of the cart?

1. Experiment: Click Reset. Place two fans on the cart, and point them in opposite directions. (Next to DIRECTION, click the button for one fan.) Turn both fans on, and click Play. What do you notice about the velocity of the cart?

1. Analyze: Select the GRAPH tab.

a. What do you notice about the graph of position vs. time (x vs t)?

Answer: It’s a straight line with a slope of two.

b. What does the velocity vs. time (v vs t) graph show?

Answer: Change in speed over time.

c. What do you notice about the graph of acceleration vs. time (a vs t)?

1. Draw conclusions: Newton’s first law states that an object in motion will travel at a constant velocity unless acted upon by an unbalanced force. How do these experiments show this?

Answer: the cart continued what it was doing unless there was an unbalanced force acting on it.

Question: How do mass and force affect acceleration?

1. Experiment: Turn on the fans. Click Play and watch the cart, then select the TABLE tab.

a. Scroll to the bottom of the table. What is the final velocity of the cart?

b. How long did it take the cart to reach the end of the track?

1. Calculate: Acceleration is a measure of how much the velocity of the cart changes each second. To calculate acceleration, divide the final velocity by the amount of time it took to reach that velocity. The units of acceleration are meters per second per second, or m/s.

a. What is the acceleration of the cart? (Include units)

3. Form hypothesis:

a. How do you think changing the mass of the cart will affect its acceleration?

Answer: The higher the mass the longer it will take to accelerate.

b. How do you think the number of fans will affect the cart’s acceleration?

Answer: The more fans the shorter the time to accelerate.

1. Experiment: Select the BAR CHART tab and turn on Show numerical values. For each of the situations below, record the acceleration of the cart.
 Load Number of fans turned on Acceleration 3 fans, 0 mass units 1 0.4 m/s^2 3 fans, 0 mass units 2 0.8 m/s^2 3 fans, 0 mass units 3 1.2 m/s^2 3 fans, 2 mass units 1 0.2 m/s^2 3 fans, 2 mass units 2 0.4 m/s^2 3 fans, 2 mass units 3 0.6 m/s^2
1. Analyze: Look at the acceleration values.

a. How did doubling the force affect the acceleration of the cart?

b. Compare the first and third lines of data. How did tripling the force affect the acceleration of the cart?

c. A cart with two mass units and three fans has twice the mass as a cart with just three fans. How did doubling the mass affect the acceleration of the cart?

1. Draw conclusions: Newton’s second law states that force is equal to mass times acceleration: F = ma. This law can be rearranged as a = F / m, or a = F ÷ m.

How does this experiment demonstrate Newton’s second law?

Answer: The simulation reflects the equation. When mass was doubled acceleration was halved, when force was doubled the acceleration was as well.

1. Challenge: The unit of force is the newton (N). One newton is the force required to accelerate a 1-kg object at a rate of 1 m/s2.

Suppose each fan supplies a force of 2 N. Use Newton’s second law and the Gizmo to find the following.

a. The mass of the cart: