Newton's First Law

An object at rest remains at rest, or if in motion, remains in motion at a constant velocity unless acted on by a net external force. This is an example of Newton's

• Second Law

• First Law

• Third Law

Which of these are examples of Newton's First Law:

1. A stationary object with no outside force will not move

2. An astronaut who has their screwdriver knocked into space will see the screwdriver continue on at the same speed and direction forever

3. If you use the same force to push a truck and a car, the car will have more acceleration than the truck because the car has less mass

4. An object at rest stays at rest

• 1,3,4

• 1,2,4

• 2,3,4

• 1,2,3

If an object is stationary, it means

• the object is in motion

• the object is not in motion

• the object is experiencing air resistance

• there are unbalanced forces acting on the object

If an object is stationary, it means

• the object is in motion

• the object is experiencing air resistance

• there are balanced forces acting on the object

• there are unbalanced forces acting on the object

_______________ is a force that counters all kinds of motion. It occurs whenever two surfaces come into contact.

• Push

• Tension

• Gravity

• Friction

The tendency of an object to resist a change in its motion is called

• inertia

• friction

• tension

• gravity

Without an unbalanced force, a moving object will not only keep moving, but its ______________________________ will also remain the same.

• force and motion

• speed and time

• speed and direction

• inertia and distance

How can you use Newton’s first law to start a skateboard to roll?

• The skateboard won’t move unless you push off from the pavement with one foot. The force you apply when you push off is stronger than the force of friction that opposes the skateboard’s motion. As a result, the force on the skateboard is unbalanced, and the skateboard moves forward.

• The skateboard won’t move unless you push off from the pavement with one foot. The force you apply when you push off is weaker than the force of friction that opposes the skateboard’s motion. As a result, the force on the skateboard is balanced, and the skateboard moves forward.

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NGSS.MS-PS2-2

How can you use Newton’s first law to stop your skateboard?

• Once the skateboard starts moving, it would keep moving at the same speed and in the same direction if not for another unbalanced force. That force is gravity between the skateboard and the pavement. The force of gravity is unbalanced because you are no longer pushing with your foot to keep the skateboard moving. That’s why the skateboard stops.

• Once the skateboard starts moving, it would keep moving at the same speed and in the same direction if not for another unbalanced force. That force is friction between the skateboard and the pavement. The force of friction is unbalanced because you are no longer pushing with your foot to keep the skateboard moving. That’s why the skateboard stops.

Which statement explains why you are thrown forward when the car you are riding in suddenly stops?

• You are pushed forward by the force of the car stopping

• The force of the crash accelerates you forward

• You are are in motion as the car is driving, and when it stops, your body continues to be in motion

• The car stopping must balance out by having you move forward