- Date:25 Jan 2020
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Get the Gizmo ready,Activity A,Click Reset,Falling objects. Select the CONTROLS tab, Question What factors affect how quickly an object falls. 1 Observe Drop each item through Air from a height of 3 meters Record how long it takes to. fall below For the tennis ball try to click Pause when it hits the ground. Shuttlecock Cotton ball Tennis ball Rock Pebble, 2 Form a hypothesis Why do some objects fall faster than others. 3 Predict A vacuum has no air How do you think the results will change if the objects fall. through a vacuum, 4 Experiment On the Atmosphere menu select None Drop each item again and record the. results below,Shuttlecock Cotton ball Tennis ball Rock Pebble.

5 Analyze What happened when objects fell through a vacuum. 6 Draw conclusions Objects falling through air are slowed by the force of air resistance. Which objects were slowed the most by air resistance Why do you think this is so. Activity A continued on next page,Activity A continued from previous page. 7 Calculate Select the Shuttlecock Check that the Initial height is 3 meters and the. Atmosphere is None Click Play and wait for the Shuttlecock to fall Select the BAR. CHART tab and turn on Show numerical values, A How long did it take the shuttlecock to fall to the bottom. B What was the acceleration of the shuttlecock during its fall. C What was the velocity of the shuttlecock when it hit the bottom. Note This is an example of instantaneous velocity, D What is the mathematical relationship between these three values. 8 Make a rule If the acceleration is constant and the starting velocity is zero what is the. relationship between the acceleration of a falling body a the time it takes to fall t and its. instantaneous velocity when it hits the ground v, Express your answer as an equation relating v a and t v. 9 Test Click Reset On the CONTROLS tab set the Initial height to 12 meters Click Play. A How long did it take for the shuttlecock to fall 12 meters. B Assuming the acceleration is still 9 81 m s2 what is the instantaneous velocity of the. shuttlecock when it hits the ground Show your work below. C Select the BAR CHART tab What is the final velocity of the shuttlecock. D Does this agree with your calculated value,Get the Gizmo ready.

Activity B,Click Reset, Terminal velocity Set the Initial height to 12 meters. Set the Atmosphere to Air, Question How does air resistance affect falling objects. 1 Observe Select the Shuttlecock Choose the BAR CHART tab and click Play What do. you notice about the velocity and acceleration of the shuttlecock. When objects fall through air for a long time they will eventually stop accelerating Their. velocity at this point is called terminal velocity. 2 Form hypothesis How will an object s size and mass affect its terminal velocity. 3 Experiment Click Reset On the CONTROLS tab select Manual settings Set the height. to 100 meters and the air density to 1 3 kg m3 close to actual air density at sea level. For each combination of mass and radius in the charts below find the terminal velocity. vterminal of the object Use the BAR CHART tab to find the terminal velocity Hint Turn on. Show numerical values,Mass Radius vterminal Mass Radius vterminal. 1 0 g 3 0 cm 10 0 g 2 0 cm,10 0 g 3 0 cm 10 0 g 5 0 cm. 50 0 g 3 0 cm 10 0 g 10 0 cm, 4 Analyze Your data show how mass and radius affect terminal velocity.

A What was the effect of increasing mass,B What was the effect of increasing radius. 5 Apply If you wanted to use a device to slow your fall what properties should it have. Get the Gizmo ready,Activity C,Click Reset,Acceleration. Select Common objects,distance and time,Set the Atmosphere to None. Question How long does it take an object to fall from a given height. 1 Observe Select the Rock and set the Initial height to 3 meters Choose the GRAPH tab. and click Play to drop the rock through a vacuum Turn on all three graphs. A What is the shape of the graph of velocity vs time. B What is the shape of the graph of acceleration vs time. 2 Analyze Select the TABLE tab and look at the v m s column. A The starting velocity was 0 m s and the final velocity was 7 68 m s Based on this. what was the average velocity of the rock, B In general how do you find the average velocity of any object falling in a vacuum. Assume you know the final velocity, 3 Calculate Distance average velocity and time are related by the equation d vaverage t.

A How much time did it take the rock to fall, B What is the product of the average velocity and time. C Does this equal the distance that the rock fell, 4 Calculate The acceleration of any object due to Earth s gravity is 9 81 m s2 For every. second an object falls its velocity changes by 9 81 meters per second For several different. times on the table multiply the time by the acceleration. A What do you notice, B If you know the acceleration and time how can you calculate the final velocity. C Challenge If you know the acceleration and time how can you calculate the average. Activity C continued on next page,Activity C continued from previous page. 5 Make a rule So far you have figured out two rules that relate time acceleration average. velocity and distance Review these rules now, A How do you find average velocity vaverage from acceleration a and time t.

B How do you find distance d from average velocity vaverage and time t. C Now put the two equations together Substitute your result in equation A for the. vaverage term in equation B Your final equation should only have d a and t terms. 6 Apply Use your rule to solve the following problems Check your answers with the Gizmo. Assume that each fall takes place in a vacuum with an acceleration of 9 81 m s2. A A rock falls for 1 43 seconds How far did it fall. B How long will it take for a rock to fall 12 meters. C A rock falls for 4 seconds How far did it fall, D A rock falls for 3 seconds What was its velocity when it hit the ground. E How long will it take for a rock to fall 50 meters. Student Exploration Free Fall Laboratory Vocabulary acceleration air resistance free fall instantaneous velocity terminal velocity velocity vacuum Prior Knowledge Questions Do these BEFORE using the Gizmo 1 Suppose you dropped a feather and a hammer at the same time Which object would hit the ground first 2

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