Forces and Shape

A woman tries to push a heavy box. The box remains stationary. Which answer best describes the forces acting on the car?

• The weight of the box is balanced by the forward force of friction.

• All forces acting on the box are balanced.

• The forward force on the box is greater than the friction between the box and the floor.

• The forces acting on the box are unbalanced.

What is the unit of force measured in?

• kg

• N

• m/s

• grams

Which of the following is not a type of force?

• gravitational pull

• kinetic

• friction

• upthrust

Which two of the following statements are true about forces?

• Forces are a vector quantity.

• Forces are measured in metres/second.

• Forces can change the shape of an object.

• Forces are a scalar quantity.

Finish the following statement:

Unbalanced forces …

• can keep an object at constant speed.

• can change the movement of an object.

• can keep an object balanced.

• always act in opposite directions.

Why does a car engine need a forward force to keep it moving at a constant speed?

• The reaction force from the car would slow it down.

• The force from the engine is needed to overcome friction.

• Gravity would make the car come to a stop.

• The force from the engine is needed to balance the force of friction and the drag forces.

A ball has fallen from a cliff edge. What are the forces acting on the ball?

• just its weight

• the reaction force from the floor

• its weight and air resistance

• only air resistance

A ball bearing is falling at constant speed through oil. What can be said about the forces acting on it?

• The weight of the ball bearing and drag forces are equal and opposite in direction.

• The weight and the drag of the ball bearing are acting in the same direction.

• Only the weight of the ball bearing is acting.

• The drag force of the oil is greater than the weight.

What is the correct definition of Hooke’s law?

• The load is inversely proportional to the extension.

• The extension decreases as the load increases.

• The extension is larger than the original length.

• The extension is directly proportional to the load applied.

Which of the following is a correct statement about a plastic material?

• It does not change shape easily.

• It breaks as soon as a force is applied.

• When the force is removed it returns to its original shape.

• It stretches before breaking.