Calculating Speed, velocity, and acceleration

Calculating Speed, velocity, and acceleration

by Leslie Dunham

​Scalars and vectors

​Different categories of measurement

Scalar quantities are described by MAGNITUDE

Vector quantities are described by both MAGNITUDE and DIRECTION

• Direction can be indicated by words (up, down, left, right, N, S, E, W) or by signs (+ or -)

Multiple Select

Which of these is a velocity? Select all that apply.

• 5 m/s

• 5 m/s, East

• -5 m/s

• 5 m/s/s

Multiple Choice

Which of the following is a vector quantity?

• Speed

• Distance

• Velocity

• Time

​Instantaneous vs. Average velocity

​Instantaneous velocity is how fast you're going in a given moment - like what you see when you look at your speedometer.

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​Average velocity is how fast you're going overall if we take your total distance over the total time.

​Velocity

​Velocity is like speed but with direction. It describes how fast something is moving and which way.

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Open Ended

What is the average velocity for a car that travels 300 meters in 45 seconds?

Open Ended

How much time would it take a car to travel 2500 meters if it has an average velocity of 15 m/s?

Open Ended

How far could a car traveling at 40 m/s go if it drives for 2000 seconds?

​Acceleration

​Acceleration occurs when an object CHANGES ITS VELOCITY

​

​This could happen when it:

​Speeds up

​Slows down

​Changes directions

​Acceleration

​Since acceleration represents a change in velocity over time, we calculate it like this

​Velocity & Acceleration

​If velocity and acceleration are in the SAME DIRECTION an object will speed up in that direction

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​If velocity and acceleration are in OPPOSITE DIRECTIONS, an object will slow down in the direction of its velocity

Open Ended

An object goes from rest to 20 m/s in 15 seconds. What is its acceleration?

Open Ended

An object has an acceleration of -5 m/s. How long will it take it to go from 20 m/s to rest?

Open Ended

An object has a velocity to the left and is speeding up. Would it's acceleration be to the left or the right?