P11 Forces (2) Friction and inertia

Early scientists described the objects slowing down as due to

• Friction

• Laziness

• Toughness

• Persistence

Before the 1600s, it was thought that to keep an object in motion would require

• No friction

• A constant force

• An inclined surface

• A flat surface

Who first described the law of inertia?

• Newton

• Galileo

• Rutherford

• Aristotle

The tendency for an object to resist changes in motion is

• Inertia

• Friction

• Laziness

• Mass

Why is the law of inertia called "Newton's first law"

• Because Newton first described it

• Because Newton included it in his book

• Because Newton figured out the math of it

• Because Newton was very famous

What does it mean when an object is 'at rest'?

• That it will slow to a stop

• That the object is lazy

• That the object is moving at a constant velocity

• That the object is not moving

Newton's first law says that an object will remain in motion at a constant velocity unless

• It is acted on by internal net forces

• It is acted on by an external force

• There is a net external force on the object

• It will always obey the law, no exceptions

An object is on a flat horizontal surface, the normal force is 25 N. What is the mass?

• 2.5 kg

• 25 kg

• 2.5 N

• 5 kg

What symbol denotes the coefficient of friction?

• N

• µ

• ∆

• F

Friction is calculated with the coefficient of friction and the

• Mass

• Height

• Normal force

• Tension