Acceleration Measures How Fast Velocity

ChangesMotion and Forces Unit

Chapter 1 Section 3

1. Speed and Acceleration Can Change with Time

Acceleration

1. Speed and Acceleration Can Change with Time (answers)

Acceleration

Describes the change of velocity over time

A rate

Is a vectorHas size and direction

Refers to any change in velocity

No acceleration if no change in velocity

2. Describe each type of Acceleration

Acceleration in the same direction as the motion

(positive acceleration)

Acceleration in the opposite direction as the motion

(negative acceleration)

Acceleration at a right angle to the motion

(acceleration in direction)

2. Describe each type of Acceleration (answers)

Acceleration in the same direction as motion

(positive acceleration)

Acceleration in the opposite direction as motion(negative acceleration)

Acceleration at a right angle to the motion

(acceleration in direction)

Speed of the object increases

Speed of the object decreases

Direction of the object changes but the speed remains the same

3. What information is needed to measure acceleration?

The change in velocity The time it took for the velocity to

change

4. What is the formula for acceleration? What units are used for each of the values?

Formula is:• Final velocity – Initial Velocity

Time Units of measure for each value are:

• Final velocity and initial velocity: meters/second

• Time: seconds• Acceleration: meters/second2, which means

(meters/second/second)

5. A skater begins skating at 1 m/s. After 4 seconds, her velocity is 3 m/s. What is the skater’s acceleration? Show your work.

Formula is:• Final velocity – Initial Velocity

Time 3 m/s – 1 m/s

4 s 2m/s /4s = 0.5 m/s/s or 0.5 m/s2

6. A car has an acceleration of 4 m/s2. What will the increase in its velocity be after 2

seconds? If it started with a velocity of 30 m/s, what is it’s final velocity?

Acceleration is 4m/s2, which means it increased it’s velocity 4m/s every second.

After 2 seconds, it would be 4 m/s x 2 seconds = 8m/s2.

It’s initial velocity was 30 m/s. It increased it’s velocity by 8 m/s

in 2 seconds so it’s final velocity is:

30 m/s + 8m/s = 38 m/s

7. Fill in the velocity – time graph below to show the velocity of a ball rolling at a constant speed of 7 m/s for 5 seconds.

0 1 2 3 4 50

1

2

3

4

5

6

7

8

Velocity (me-ters/second

Time (seconds)

Velo

cit

y (m

ete

rs/s

econ

d)