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Author:
Jack Bauer

Student Exploration: Gravity Pitch

Vocabulary: escape velocity, gravity, orbit, orbital velocity, trajectory, velocity

Prior Knowledge Questions (Do these BEFORE using the Gizmo.)

On their summer vacation, a family is standing at a scenic overlook at the top of a tall cliff. Young Alice (age 2) tosses a rock over the edge and giggles as she watches it fall. Brother Darrell (age 8) thinks he can do better and hurls another rock over the edge. Papa Billy chuckles, picks up a nice round rock, and flings it off the cliff as hard as he can.

1. In the picture to the right, draw the trajectory, or path, that each rock would take. Label the three trajectories “Alice”, “Darrell” and “Billy” (or just A, D and B).

2. What would happen if Billy could throw the rock as fast as a rocket?.

Gizmo Warm-up: Which way does gravity pull?

1. Use the slider to set the Velocity to 0.0 km/s (kilometers per second). Velocity is basically the same thing as speed, but has direction as well. In this case the pitcher is simplydropping the ball. Click Play ( ).

A. What direction does the ball go?

B. Sketch the pitcher and the trajectory of the ball on the diagram.

2. Click Reset ( ) and drag the pitcher to several new positions. Click Play and watch him drop the ball each time. Sketch the pitcher and the trajectory of each ball on the diagram.

A. What do you notice?

B. The ball is pulled by a force called gravity. In what direction does gravity always pull the ball?.Activity A: How far does it go?

Get the Gizmo ready:

Click Reset.Drag the pitcher back to the top.Get the Velocity to 1.0 km/s (2,232 miles per hour).

Question: Why do objects go around, or orbit, other objects?

1. Observe: Click Play and observe the ball’s trajectory. (Note:The pitcher is very tall – about 1500 km (930 miles) tall!)2. Predict: How would the trajectory of the ball change as the pitcher throws it harder and harder? Explain below, and draw several predicted trajectories on the diagram..

3. Collect data: Throw the ball at velocities of 3, 5, and 7km/s. If necessary, use the Fast forward button ( ) to speed things up and the “–” zoom control to see a larger area. For each throw, sketch and label the trajectory and record the Distance traveled in the table below.

4. Analyze: What happens?

Tutorial