Laws of Motion

Mr. Dunnum

Physical Science

Key terms

MotionSpeedAverage SpeedInstantaneous SpeedVelocityAcceleration

What is motion?

Motion is when an object of any sort is changing positions

Fast moving airplane Swirling of the wind Trickle of water

Distance and Displacement

• Displacement includes the distance between the starting and ending points and the direction in which you travel.

This figure shows the difference between distance and displacement

What is speed?

Speed is the distance traveled divided by the time taken to travel the distance

Olympics runners run the 100m in 10s, which equals 10m/s or meters per second

Video

Practice problem

Calculate the speed of a swimmer who swims 100 m in 56s

What you know: Distance: 100m Time: 56sEquation: Speed= distance/timePlug it in: Speed= (100)/(56)Answer: Speed=1.8m/s

Problem

A runner completed a race of 400 m in 43.9s. In a 100m race he finishes in 10.4s. Which race was his speed faster.

100=9.6 m/s

Average Speed

Average speed is found by dividing the total distance traveled by the time taken

Intermediate sprinterNever runs the race at the same speed

the entire time so you will have to get an average speed.

A trip to Atlanta

Instantaneous Speed

When an object is in motion it changes speeds many different times

The speed of an object at one instant of time is instantaneous speed

For example a car accelerating 0-60 in 5 secs

Velocity/Acceleration

Velocity

The velocity of an object is the speed of the object and direction of its motion

Car traveling n 60mph then turns west and continues at 60mph. Does the velocity change?

Acceleration Means simply a change

in velocity Acceleration is more

than speeding up Acceleration is not how

much velocity changes but how fast.

Video

Examples of acceleration/velocity

Examples of acceleration Examples of velocity

A plane taking off Increase in speed

A car stopping at a stop sign Decrease in speed

Jogging a winding trail Change in direction

Driving around a corner “

Standing on the Earth’s equator “

Rocket launching “

Examples of acceleration/velocity

Examples of acceleration Examples of velocity

A plane taking off Increase in speed

A car stopping at a stop sign Decrease in speed

Jogging a winding trail Change in direction

Driving around a corner “

Standing on the Earth’s equator “

Rocket launching “

Calculating acceleration

Acceleration= final velocity- starting velocity time it takes to change velocity

A plane passes over point A with a velocity of 8000m/s north. 40 sec. later it passes over Point B at a velocity of 10,000 m/s north. What is the acceleration from A to B.

50m/s/sNegative acceleration is also called decceleration