Student Exploration: Fan Cart Physics

Vocabulary: acceleration, force, friction, mass, newton, Newton’s first law, Newton’s second law, Newton’s third law, velocity 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? The speed of the cart would be slow/decrease 2. Suppose several more horses were hitched up to the same cart. How would this affect the speed of the cart? The speed would increase 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? The air is pushed towards the left (negative). 2. Press Play ( ) and observe the cart. In which direction does the cart move? The cart is moving towards the right 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. 3. 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? The velocity changes (its gets higher) A change in velocity is called acceleration (a). This study source was downloaded by from CourseH on :23:44 GMT -06:00 2019 Activity A: Newton’s first law Get the Gizmo ready:  Click Reset.  Remove all fans from the cart. 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? (There is no friction in this model.) The cart would remain where it is (at rest) unless acted upon by an external force. This is known as Newtons first law of motion. 2. 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? The velocity of the cart when it reaches the wall would be 20m/s because Newtons 3rd law of motion states that for every action (force) in nature there is an equal and opposite reaction. 3. 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? The velocity of the cart is constant. 4. 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? The velocity of the cart is constant. 5. Analyze: Select the GRAPH tab. A. What do you notice about the graph of position vs. time (x vs t)? The graph has a straight line which means that position and time have a constant relationship. B. What does the velocity vs. time (v vs t) graph show? The velocity versus the time graph shows us a constant velocity. C. What do you notice about the graph of acceleration vs. time (a vs t)? The graph of acceleration versus time shows us an acceleration of 0 which means that the velocity is not changing. 6. 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? This study source was downloaded by from CourseH on :23:45 GMT -06:00