Acceleration, Speed, and Velocity

AccelerationAcceleration is a change in

velocity by Changing speed:

▪ Starting▪ Stopping▪ Speeding up▪ Slowing down

Or changing direction

Acceleration Acceleration can be positive or negative

Speeding Up – Positive acceleration (+) Slowing Down – Negative acceleration (-)

Units – measured in m/s2

Acceleration is caused by unbalanced forces Calculating Acceleration:

Final Speed – Initial Speed Time

Speed A way to describe motion.

Average speed - Rate of motion calculated by dividing the distance traveled by the amount of time it takes to travel that distance

Constant speed - Speed that does not change

Instantaneous speed - Speed of an object at any given time

Units: Measured in m/s

Instantaneous vs. Average Speed

What is the formula used to calculate speed?

Speed is calculated by dividing distance by time.

What is the formula for calculating speed?

Distance Time

Speed =

Calculating SpeedGiven Distance & Time

Divide Distance by TimeDistance ÷ Time = SpeedSpeed = Distance ÷ Time

Calculating DistanceGiven Speed & Time

Multiply Speed and TimeDistance = Speed X TimeSpeed X Time = Distance

Calculating TimeGiven Distance and Speed

Divide Distance by TimeDistance ÷ Speed = TimeTime = Distance ÷ Speed

Calculate this Speed

A football field is about 100 m long. If it takes a person 20 seconds to run its length, how fast was the football player running?

A football field is about 100 m long. If it takes a person 20 seconds to run its length, how fast was the football player running?

Speed = Distance ÷ Time

Speed = 100 m ÷ 20 sSpeed = 5 m/s

Remember to include

the UNITS!!

Calculate this Speed:

Velocity Velocity is speed with direction   Calculating velocity is the same as

calculating speed (distance/time).   The difference is that velocity is what

physicists call a vector. There must be direction.

Speed = 3 m/s Velocity = 3 m/s, heading northeast

Velocity = Final Distance – Initial Distance                     Final Time – Initial TimeVelocity = Final Distance – Initial Distance                     Final Time – Initial Time

Distinguish between Speed and VelocitySpeed describes distance and time

Velocity describes distance, time, and direction

You can say the top speed of an airplane is 300 kilometers per hour (kph). But its velocity is 300 kph in a northeast direction.

Let’s PracticeWhich of the following sentences contain an example of velocity and which contain an example of speed?

A. Five seconds into the launch, the rocket was shooting upward at 5000 meters per second.

B. Cheetahs can run at 70 miles per hour.

C. Moving at five kilometers per hour, it will take us eight hours to get to the base camp.

D. The car covered 500 kilometers in the first 10 hours of its northward journey.

E. Roger Bannister was the first person to run one mile in less than four minutes.

Velocity

VelocitySpeed

Speed

Speed

Summarizing Podcast

Velocity

TimeDistance

m/s

m/s2

Speed

Acceleration

Direction

• Time• m/s• m/s north• m/s2

• Distance• Direction

m/s north