Acceleration

Vector Diagrams Continued…The magnitude (speed)of a vector quantity is represented by the size of the vector arrow. If the size of the arrow in each vector diagram is the same, then the speed is constant. If the size of the velocity vector is increasing, then the object is accelerating.

Check Your Understanding

Object is slowing down

Object is Speeding up

Acceleration

Acceleration- the rate at which velocity changes over time. An object accelerates if it changes speed or direction.

The position vs. time graphs for the two types of motion - constant velocity and changing velocity acceleration- are depicted as follows.

Acceleration: Position Time Graph

Note that a motion described as a changing, positive velocity results in a line that curves and positive slope when plotted as a position-time graph.The mathematical equation to calculate the acceleration is quadratic ax+bx+c2

Acceleration: Velocity Time Graph

The car moving with a changing velocity- that is, a car that is moving rightward but speeding up or accelerating. Since the car is moving in the positive direction and speeding up, the car is said to have a positive acceleration.

Acceleration Formula

Acceleration = Final Velocity- Initial Velocity Time it takes to change speed

A =Vf - Vi

T

Calculate it #1

Given Work

Answer

Vi

T =

Vf=

Vi=

Vf- Vi

TA = A = 220 km/hr- 0 km/hr

22s

10 km/hr

22 s0 km/ hr

220km/hr

TVf

A= ?

A

Calculate It #2Lillian has had enough of Tiffany’s antics and high jinks and walks over to Tiffany’s table. With an initial speed of 2 m/s, Lillian accelerates at a rate of 18 m/s/s for 1.5 seconds, what is her final speed?

Given Work

Answers

Vi

A TVf

Vi=Vf=T=

A=

2 m/s

18 m/s/s1.5 s? A =

Vf- Vi

T 18 m/s/s = ? - 2 m/s 1.5 s

(1.5)(1.5)27= ?-2 m/s

29 m/s

Calculate It #3Connor dribbles the ball from one end of the court to the other. With an initial speed of 0 m/s and final speed of 14 m/s, he accelerates at a rate of 2 m/s/s. How long does it take Connor to get from one end of the court to the other?

ViVf

TA

Given Work

Answers

Vf=Vi=A=T=

0 m/s14 m/s2 m/s/s?

2 m/s/s =14m/s - 0 m/s

???

2 m/s/s =2 m/s/s =

7 seconds