lesson #7

Lesson #7

E.Q: What the increasing and decreasing of velocity means?

What is Acceleration

● Acceleration is the change in velocity per unit time.
● Acceleration can result from

A change in speed (increase or decrease)

A change in direction (up, down, back, forth...)

Changes in both

Mr. Posada’s
Bugati

Formula

Acceleration =

Change in velocity

Change in time

a = Δv

Δt

vf - vi

=

Δt

Ariel dropped a golf ball from her second story window.

The ball starts from rest and hits the sidewalk 1.5 s later
with a velocity of 14.7 m/s. Find the average acceleration
of the golf ball.
vf - vi

Δt

14.7 m/s - 0 m/s

1.5 s

a =

= 9.8 m/s2

Multiple Choice

What are the units for acceleration?

• m/s²

• m

• sec

• s/m

Carlos’s car accelerates from 30m/s (V_i) to 60 m/s (v_f)

northward in 15 seconds. What is the
acceleration of the car?

vf - vi

Δt

60 m/s - 30 m/s

15 s

a =

=

2 m/s2

Carlos’s car accelerates from 60m/s to 30 m/s

northward in 15 seconds. What is the
acceleration of the car?

vf - vi

Δt

30 m/s - 60 m/s

15 s

a =

=

-2 m/s2

Notice the negative sign! It means
the car is slowing down

Acceleration Graph

Match

Match the following graphs to the right description.

Speeding up

No acceleration (constant speed)

Slowing down

• Speeding up

• No acceleration (constant speed)

• Slowing down

What part of the graph shows no
acceleration?

What part of the graph shows the highest
acceleration?

Multiple Choice

What is the acceleration in the first ten seconds?

(15m/s - 0m/s) / 10s =

• 4 m/s2

• 1.5 m/s²

• 10 m/s2

• 0 m/s2

Multiple Choice

In which part of the graph is the object slowing down?

• A

• B

• C

• D

Draw

Draw a line that shows an object moving in constant velocity/speed.

Multiple Choice

What is the average acceleration at 30 seconds, according to the graph?

• 0.833 $$\frac{m}{s^2}$$

• 25 $$\frac{m}{s^2}$$

• 1.2 $$\frac{m}{s^2}$$

• 15 $$\frac{m}{s^2}$$

Multiple Choice

Karina is slowing down on her skateboard. She starts at a speed of 5.5m/s and slows to 1.0 m/s over a time of 3.0 seconds. What is Karina's acceleration?

• -1.5 $$\frac{m}{s^2}$$

• 8.5 m/s

• -2.5 m/s

• 4.5 km/s

Multiple Choice

A roller coaster's velocity at the top of a hill is 10m/s. 2 seconds later, it reaches the bottom of the hill with a velocity of 26 m/s. What was the acceleration of the coaster?

• 20 m/s

• 10 m/s2

• 8 $$\frac{m}{s^2}$$

• 16 m/s3