Understanding AccelerationAccelerationCalculating Acceleration

I. The Acceleration EquationA. Acceleration – a measure of how quickly something speeds up,

or slows down, or changes direction1. Positive Acceleration – means that the velocity is increasing in the

forward direction (speeding up forward)2. Negative Acceleration – means that the velocity is decreasing in

the forward direction (slowing down forward)B. What is involved in the acceleration equation?

1. My truck is really fast, it can go from 0mi/hr – 60mi/hra. What’s missing in the above statement?

i. The time it takes to go from 0mi/hr – 60mi/hr

2. Acceleration then must include how much you speed up or slow down and the time it takes

C. For example if it takes my truck 6s to speed up from 0 to 60mi/hr, it must be speeding up by 10mi/hr every second.

1. Its acceleration is:

shr

mihr

mi10 or s

10

I. The Acceleration Equation

D. The Equation for acceleration is:

E. Mathematically, the equation is written as:

Timein Change

yin velocit Changeonaccelerati

t

Va

Next Comesr in Whateve Change Means Δ

Comprehension Check

A. What are the three ways that an object can accelerate?1. Speed up; Slow down; Turn

B. Indicate whether each object below is accelerating or not.1. Car turning a corner without slowing down or speeding up.

a. Accelerating (changing direction)

2. A basketball right after it is tossed into the air.a. Accelerating (slowing down)

3. A car driving on a straight interstate with its cruise control on.a. Not accelerating (not turning, speeding up, or slowing down)

4. A water balloon right after it is dropped from a balcony.a. Accelerating (speeding up)

5. A kid sliding along the floor in his or her socks.a. Accelerating (slowing down)

Basketball Acceleration Post Lab Questions

6. What does the slope of distance versus time graph tell us?• The slope tells us the velocity (the speed and direction) of the

object.7. When the graph’s slope is curving, was the basketball

accelerating or moving steadily?• Since the velocity changes when the graph curves the basketball is

accelerating.8. When the slope is straight, was the basketball accelerating or

moving at a steady velocity?• A straight slope means constant velocity. The velocity from the

tangent button barely changes at all.

Basketball Acceleration Post Lab Questions

Distance Versus Time for Basketball Video

0.00

1.00

2.00

3.00

4.00

0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60

Time (s)

Dis

tanc

e (m

)

I

IIV

IVIII

VI

-Slope increases from zero to a large positive slope-Speeding up forward

-Constant positive slope-Constant forward velocity

-Slope decrease from a large positive slope to zero-Slowing down forward

-Slope increases from zero to a large negative slope-Speeding up backwards -Constant

negative slope-Constant backward velocity -Slope

decrease from a large negative slope to zero-Slowing down backward

Basketball Acceleration Post Lab Questions

10. Using the Tangent data and the video, what was happening to the velocity of the ball when it was touching the hands of the thrower?

1. The ball was either speeding up or slowing down. That is it was accelerating.

11. What was happening to the ball when it was not touching the hands of the throwers?

1. The slope and velocity was constant when it was flying through the air.

12. Looking at the screen what happens to the spacing of the dots at high velocity compared to small velocities?

1. The dots are closer together when the ball is moving slowly because the ball is covering less distance every frame.

13. Sketch a graph for each of the following scenarios.

Comprehension Check

A. Identify each of the following objects as either accelerating or not accelerating

1. Mike is jogging down the street at 3m/sa. No acceleration – straight line and constant speed

2. Joe is applying the brakes as rides his bikea. Negative acceleration

3. Sarah jogs around the track at a constant speeda. Acceleration, changing direction

4. Michelle sits down and then sprints to catch upa. Positive Acceleration – speed is increasing

5. The earth orbits the suna. Acceleration – changing direction

II. Example Problem 1

A. A Dodge Viper can go from 0mi/hr to 60mi/hr in 3.5s. What is the acceleration of the car?

t

Va

shr

mihr

mi1.173.5s06

a

ΔV =

Δt =

a =

60mi/hr

2.7s

?

This means that the velocity of the car is increasing by17.1 mi/hr every second.

III. Example Problem 2A. Sharon, a skydiver, can reach velocities of 55.0m/s

while in freefall, which means she is traveling the length of a football field in 2s. Once she deploys her parachute, it takes her 2.7s to slow down to her landing velocity of 3.2m/s. What is Sharon’s acceleration?

t

Va

2.7s

8.51 sm

ΔV =

Δt =

a =

3.2m/s – 55.0m/s= -51.8m/s

?

The negative sign indicates that the velocity is decreasing at a rate of 19.2m/s every second.

2.7sss

sms

m

2.192.19

IV. Solving for ΔVA. In a vacuum, all objects near the Earth’s surface

accelerate at 9.81m/s/s. If a water balloon is dropped from a balcony and falls for 2.9s, what was its change in velocity?

Δt

ΔVa t

t

Vta

ΔV=

Δt=

a=

?

2.9s

-9.81m/s2

taV sm

sm 4.28)81.9)(s9.2( 2

V. Solving for ∆tA. How long does it take the shuttle to slow down

from 28,200km/hr to its landing velocity of 352km/hr if it’s acceleration is -879km/hr/min?

t

Va

tt

Vta

ΔV=

Δt=

a=

28,200km/hr - 352km/hr = 27,848km/hr

?

-879km/hr/min

a

V

a

ta

Vta

a

Vt

min7.31

879

848,27

min

hrkm

hrkm