Forces (Part 3)

When writing with a pencil is friction useful or harmful?

• Useful

• Harmful

Will the magnets attract or repel?

• Attract

• Repel

Look at the picture of the skydiver. In which direction does the force of gravity act on him?

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• 
• 
• 

Look at the picture of the skydiver. In which direction does the force of air resistance act on him?

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• 
• 
• 

Look at the picture of the skydiver. Are the forces acting on him balanced or unbalanced?

• balanced

• unbalanced

Look at the picture of the skydiver. Which force is greater?

• weight

• push

• compression

• air resistance

Look at the picture of the skydiver. Are the forces acting on him balanced or unbalanced?

• balanced

• unbalanced

Look at the picture of the skydiver. The arrows are equal in size. What does this mean?

• The force of gravity and the force of air resistance are balanced so that the skydiver deaccelerates (reduces speed) while falling.

• The force of gravity is greater than the force of air resistance, so the skydiver deaccelerates (reduces speed) while falling.

• The force of gravity is less than the force of air resistance, so the skydiver accelerates (increases speed) while falling down.

• The force of gravity and the force of air resistance are balanced, so the skydiver falls down at a steady velocity (same speed).

Observe the picture carefully. What does it show?

• elastic formation

• plastic formation

• elastic deformation

• plastic deformation

A force of 100 N is applied with a finger. Which picture shows a larger pressure exerted on the wood, A or B? Why?

• Picture A shows a larger pressure exerted because of larger area in contact with the wood.

• Picture B shows a larger pressure exerted because of larger area in contact with the wood.

• Picture A shows a larger pressure exerted because of smaller area in contact with the wood.

• Picture B shows a larger pressure exerted because of smaller area in contact with the wood.