6 - Unit 4, Section 1 - Day 1

Forces

Unit 4, Section 1

• Force - a push or a pull

  • You pull a door open

  • You push a basketball as you make a shot

• Newton (N) - the metric system unit of force

Forces

• Remember, velocity is the distance an object moves divided by the time it took to move that distance

• It's measured in meters per second

Velocity

Multiple Choice

A car moves a distance of 300 meters in 7.5 seconds. What is the car's velocity?

• 40 m/s

• 0.025 m/s

• 2,250 m/s

• 300 m/s

• Acceleration - a change in velocity divided by the time it took that change to occur

• It's measured in meters per second squared

Acceleration

Multiple Choice

A car speeds up from 20 meters per second to 45 meters per second in 10 seconds. What is the car's acceleration?

• 2.5 meters per second squared

• 2 meters per second squared

• 4.5 meters per second squared

• 25 meters per second squared

Answer the following question in your guided notes:

• Which is harder to stop: a shopping cart moving at 15 m/s or an SUV moving at 15 m/s?

Quickwrite

Inertia - a tendency to resist a change in motion

• An object that's moving is difficult to stop

• An object that's not difficult is hard to start

Inertia

• An object in motion will remain in motion, and an object at rest will remain at rest, until a force acts upon it

• Also called The Law of Inertia

Newton's First Law of Motion

• Wait

• If you roll a ball down the hall, it'll eventually stop

• What's slowing it down?

• Friction - a force that resists motion between two surfaces that are in contact

Friction

• When an object is acted on by a net force, it causes a change in velocity in the direction of the force

• A force causes an acceleration

Newton's Second Law of Motion