8th Gr. Unit 3 1-2

After observing the magnetic cannon phenomena, Sanjan had the following questions. What questions do you think his classmates can investigate in the classroom? Select all that apply. 

• Does the incoming ball speed up as it nears the magnet?

• Would this cannon work using balls of another material?

• Since the magnets pull the balls toward them, what pushes the outgoing ball away?

• How would this work with stronger magnets?

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What energy conversions and transfers are associated with Newton’s Cradle? Select all that apply.

• The KE from the last ball is converted to gravitational energy.

• Gravitational energy is transferred from the balls to the surrounding air.

• The kinetic energy is transferred from one ball to the next ball and the next ball until the last ball.

• When a ball is lifted and released, gravitational energy is converted to kinetic energy.

• When the ball hits another ball, kinetic energy is transformed into elastic energy and then transferred to the next ball, and the next. Elastic energy is transformed into kinetic energy and transferred to the last ball.

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 Consider the magnetic cannon as a system. What are all of the components (or parts) of the system? 

• The rulers and the ball bearings

• The magnets and rulers

• The rulers, the steel ball bearings, table, and the magnet

• The magnet and steel ball bearings

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Why is the box, sitting on the table, not moving?

• No forces are acting on the box.

• The table pushes up with the same force that gravity pulls down.

• Gravity is keeping the box down on the table.

• Gravity is pulling down, but the table is in the way.

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 The image is an example of a contact force. What statement below is true regarding contact forces?

• If one force is a push, the other will also be a push; if one is a pull, the other will also be a pull.

• Contact pairs always act in the same direction.

• Contact pairs always act in opposite directions.

• When two objects are touching, one force is always stronger than the other force.

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The diagram represents a stuck vehicle.

What are all of the components of this system?

• Vehicle 1, vehicle 2, and the rope.

• Vehicle 1 and vehicle 2.

• Vehicle 1, rope, vehicle 2, and the ground.

• The rope and the ground only.

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The diagram represents a stuck vehicle.

What do we know about contact forces as represented in the diagram?

• Contact forces come in groups of 3 and act in opposite directions.

• Contact forces can be from 1-3 objects. Sometimes they act in the same direction but other times they act in opposite directions.

• Contact forces come in pairs and act in opposite directions.

• A contact object  touches one to three other objects and acts in a variety of directions.

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The force between Earth and other objects is different from contact forces - whether or not you are in contact with the Earth, the reason for the force is not contact, rather it is gravity. Gravity is called a force that acts at a distance. What other forces act at a distance? Check all that apply.

• Magnetic forces also act at a distance and come in pairs.

• Friction is a force that acts at a distance but is stronger the closer the objects.

• Magnets do not have to be in contact with each other to apply a force to the other.

• The electrical force from a balloon attracting pieces of paper from a distance to the balloon.

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We can now refer to the vehicle-pull-vehicle diagram as a model since it can be used to explain and predict the system’s behavior.  Which model shows forces acting at a distance correctly? 

• 
• 
• 

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Identify the forces acting [A, B, & C] within the floating magnets system. 

• A = Magnetic Force, B = Contact Force,  C = Gravitational Force

• A = Magnetic Force, B and C are contact forces

• A, B, and C are all contact forces.

• A and C = Gravitational Force, B = Contact Force

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