Brittany Moore8/29/12

Understanding Motion

motion: movement

What two things are important in describing motion:DistanceTime

Do you have to see something literally move to know its in motion?

What is motion?

Distance: how far something has movedMeters (m), kilometers (km)

Displacement: distance and direction of an object’s change in position from the starting point

What are the differences between distance and displacement?

Distance vs. Displacement

Speed: distance an object travels per unit of timeHow do we calculate speed?

Speed = distance/time

Ex: A car traveling at a constant speed covers a distance of 750 m in 25 s. What is the cars speed?

Speed

A passenger elevator travels from the first floor to the 60th floor, a distance of 210 m, in 35 s. What is the elevators speed?

A motorcycle is moving at a constant speed of 40km/h. How long does it take the motorcycle to travel a distance of 10km?

More examples of speed

Does your car always run at a constant speed?

What might a graph of your car’s speed look like on a typical day to school?

Can speed change over time?

Average speed: total distance traveled divided by the total time of travelEx: A runner travels 100 m in 30 s. What is

their average speed?

Instantaneous speed: speed at a given point of timeEx: On my way to school I look down to see

that I am travelling 136.8 km!

Types of Speed

What kind of graph would be best to show motion? Distance over an amount of time…

How does the steepness of a line effect the speed?Speed = slope

How are graphs used?

Example

Lets have a race…can you calculate your speed?Speed = distance / time = m / s

Work in groups to complete worksheet.

Yay for Outside!

Velocity: speed of an object and the direction of its motion

The velocity of an object can change even if the speed of the object stays the sameEx: BMS—the race car has a constant speed

and is going around an oval track; even though the speed remains constant, the velocity changes because the direction of the car’s motion is changing constantly

Velocity

Example

Acceleration: the rate of change of velocityAcceleration occurs when an object changes its speed,

direction, or both.

Change in velocity = final velocity – initial velocityAcceleration = Vf – Vi Units in m/s

2

tEx: Speeding up and slowing down.

As a car speeds up: positive velocity, acceleration, and speed.

As a car brakes: positive velocity, negative acceleration (deceleration) and decreasing speed.

Acceleration

Don’t athletes have to make quick changes in acceleration?

Can you think of any equipment used by athletes to help with this?

Connections…

Yes! Examples include:

-starting blocks for runners-cleats on shoes-rubber soled shoes -special clothing

Force: push or pull on an object; changes in the movementEx: hitting a tennis ball, gravity on your body,

pool, etc.

Force = mass x acceleration

What is force?

Net force: when two or more forces act on an object at the same timeBalanced: equal forces acting in opposite

directionUnbalanced: unequal forces acting in opposite

direction

Net Force

Newton’s Laws of Motion