MOTIONIntroduction

MOTION

Motion is defined as when an object changes position over time when compared to a reference point.

A reference point is an object that appears to stay in place.

The Earth’s surface is a common reference point when comparing objects. Other common reference points are trees or buildings. A moving object can also be used as a reference point.

SPEED

The rate at which an object moves depends on the distance traveled and the time taken to travel that distance

Speed is the rate at which an object travels

Ex: It took 10 seconds to travel 50 meters

Speed = distance/time

= 50 meters/10 seconds

= 5 m/s

AVERAGE SPEED

Most of the time objects don’t travel at a constant speed, but change speed. Think of when you’re riding a bike or driving a car somewhere. There are turns, stop signs, and traffic lights.

Average speed is the total distance traveled over the total time

Average speed = total distance/total time

PLEASE SOLVE:

If you walk for 2 hours and travel 500 meters per hour, what is your speed?

It takes you 10 hours to drive to Vermont and you travel 500 miles, what is your speed?

If you run for 1 hour and travel 6 miles, what is your speed?

If you walk for 1.5 hours and travel 7.5 kilometers per hour, what is your average speed?

A plane flies at a speed of 150 m/s for 10 s and 200 m/s for 5 s, what is the plane’s average speed?

VELOCITY

The speed of an object in a particular direction

Changes when speed or direction changes, or both

Speed change: 15 m/s South to 20 m/s South

Direction change: 15 m/s South to 15 m/s East

Speed and direction change: 15 m/s South to 20 m/s East

SPEED VS. VELOCITY

What’s the difference?

Speed is the amount of time it takes an object to travel a certain distance

Velocity is the amount of time it takes an object to travel a certain distance in a certain direction

RESULTANT VELOCITY Velocity combines If you’re riding in a bus traveling 15 m/s East and

you stand up to walk down the aisle to the front while it is moving, are you still moving at the same velocity as the bus?

If the bus is traveling 15 m/s East and you stand up to walk down the aisle to the front at 1 m/s East, what is your resultant velocity?

If you’re riding the same bus traveling 15 m/s East and you stand up to walk down the aisle to the back at 1 m/s West, is your resultant velocity the same as above? What is your resultant velocity?

ACCELERATION

The rate at which velocity changes

Acceleration = final velocity – starting velocity/time it takes to change velocity

PLEASE SOLVE

A bird passes over point A with a velocity of 500 m/s North. 40 seconds later it passes over point B at a velocity of 10,000 m/s North. What is the plane’s acceleration from point A to point B?

A plane passes over New York with a velocity of 8,000 m/s North. An hour later it passes over Boston at a velocity of 9,000 m/s North. What is the plane’s acceleration from New York to Boston?

A coconut falls from the top of a tree and reaches a velocity of 19.6 m/s when it hits the ground. It takes 2 seconds to reach the ground. What is the coconut’s acceleration? What is the speed at which the coconut is traveling after 1 second of falling?