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# 180 - PowerPoint PPT Presentation

Define MOTION. 60. 140. 130. 120. 40. 50. 30. 10. 70. 8. 7. 6. 5. 9. 4. 3. 2. 0. 180. 80. 20. 90. 160. 150. 170. 100. 110. 1. Seconds Remaining:. Motion : Change in position of an object relative to a reference point. Describe SPEED and VELOCITY. 1. 50. 140.

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Define MOTION

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Motion:

Change in position of an object relative to a reference point.

Describe SPEED and VELOCITY

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• SPEED - is the rate of motion, or the rate of change of position;

• a measurement of distance traveled over time

• calculated by dividing the distance traveled by the time taken

• VELOCITY - measurement of the rate and direction of motion

• an object's speed and direction of motion

Describe Friction

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FRICTION - the resistance to motion encountered when one body is moved in contact with another

Force opposing motion of two objects that are in contact.

Describe ACCELERATION

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• ACCELERATION - The rate at which an object's velocity changes with time.

• The rate of change of velocity.

• Change in speed or change of direction.

Create a diagram of a distance-time graph and a velocity-time graph

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A student stands on a skateboard as the skateboard remains in place. When the student pushes his foot against the ground, the skateboard moves forward. The harder he pushes against the ground, the faster the skateboard moves. A friend jumps on for a ride, and the skateboard slows down. The student must push even harder to get the skateboard moving again. Once they get going, they hit a curb. The skateboard stops moving, but the students fly onto the grass. Fortunately, everyone is fine.– Describe three instances in the above paragraph where the skateboard was under the influence of unbalanced forces. For each instance, identify the primary forces involved, and explain why they were unbalanced.

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Three situations where the skateboard is under the influence of unbalanced forces are:1. The student giving the initial push to move the skateboard — unbalanced between acceleration by the student and friction, as the skateboard started moving.2. Friend jumps on the skateboard — unbalanced between acceleration by the student and friction, as the skateboard started slowing down.3. Hitting the curb — unbalanced between acceleration by the student and force exerted by the curb, as the skateboard stops moving.

A group of students split up into two groups of four for a tug-of-war. Each group pulls on one end of a heavy rope.– Draw a diagram showing what happens when the forces on the rope are balanced. The forces involved should be represented by arrows, and any motion should be drawn and labeled. Your diagram should include the students pulling on the rope.

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A person jumps out of an airplane. At first, the person speeds up during the fall. But then, the person falls at a constant velocity known as terminal velocity. – Identify the two primary forces acting on the person during the fall.

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The person experiences the primary forces of gravity and air resistance during the fall.

Explain inertia

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An object in motion will remain in motion (keep moving), and an object at rest will remain at rest (not move) unless acted upon by an outside force.

A student stands on a skateboard as the skateboard remains in place. When the student pushes his foot against the ground, the skateboard moves forward. The harder he pushes against the ground, the faster the skateboard moves. A friend jumps on for a ride, and the skateboard slows down. The student must push even harder to get the skateboard moving again. Once they get going, they hit a curb. The skateboard stops moving, but the students fly onto the grass. Fortunately, everyone is fine.– Describe three instances in the above paragraph where the skateboard was under the influence of unbalanced forces. For each instance, identify the primary forces involved, and explain why they were unbalanced.

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Three situations where the skateboard is under the influence of unbalanced forces are:1. The student giving the initial push to move the skateboard — unbalanced between acceleration by the student and friction, as the skateboard started moving.2. Friend jumps on the skateboard — unbalanced between acceleration by the student and friction, as the skateboard started slowing down.3. Hitting the curb — unbalanced between acceleration by the student and force exerted by the curb, as the skateboard stops moving.

A student stands on a skateboard as the skateboard remains in place. When the student pushes his foot against the ground, the skateboard moves forward. The harder he pushes against the ground, the faster the skateboard moves. A friend jumps on for a ride, and the skateboard slows down. The student must push even harder to get the skateboard moving again. Once they get going, they hit a curb. The skateboard stops moving, but the students fly onto the grass. Fortunately, everyone is fine.

Describe one instance in the above paragraph where the skateboard was under the influence of balanced forces. Identify the primary forces involved, and explain why they were balanced.

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A situation where the skateboard is under the influence of balanced forces is:1. The student standing on the skateboard as it remains in place — balanced between gravity and force exerted by the ground, as the skateboard remains motionless.

The speed of a person riding a bicycle on a level, straight road is measured and plotted in the above graph.– Identify and describe the two primary factors acting on the bike that affect its speed for each of the following time periods:   – 0 min. to 1 min.   – 1 min. to 2 min.

– 2 min .to 3 min.   – 3 min. to 4 min.

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Acceleration by the biker and the friction are the primary forces acting on the bike that affect its speed.

During period 1, the forces are unbalanced, because the bike is slowing down.

During period 2, the forces are balanced, because the bike's speed stays constant.

During period 3 the forces are unbalanced, because the bike is speeding up.

During period 4, the forces are balanced, because the bike's speed stays constant.

In what direction is the force of friction exerted?

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The force of friction is exerted opposite to the direction of motion

What are two ways you can change your velocity?

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Change speed or change direction

What is a net force?

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A net force is the sum of the forces acting on an object

Describe work

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Work is done when a force causes an object to move in the direction of the force.