AP Physics 1


 

 

Distance and Motion
St. Mary's HS

 

 

C. Acceleration - time rate of change in velocity (how quickly velocity is changing)

 

 

Which car has the greater acceleration?

t(sec) t = 0 t = 1 t = 2 t = 3 t = 4 t = 5
Car A 70 m/s 72 m/s 74 m/s 76 m/s 78 m/s 80 m/s
Car B 0 m/s 3 m/s 6 m/s 9 m/s 12 m/s 15 m/s
Car C 90 m/s 90 m/s 90 m/s 90 m/s 90 m/s 90 m/s
Car D 100 m/s 99 m/s 98 m/s 97 m/s 96 m/s 95 m/s

 

 

 

 

 

Car A

 +2 m/s/s

Car B

 +3 m/s/s

Car C

 0 m/s/s

Car D

- 1 m/s/s


t(sec) t = 0 t = 1 t = 2 t = 3 t = 4 t = 5
Car A 70 m/s 72 m/s 74 m/s 76 m/s 78 m/s 80 m/s
Car B 0 m/s 3 m/s 6 m/s 9 m/s 12 m/s 15 m/s
Car C 90 m/s 90 m/s 90 m/s 90 m/s 90 m/s 90 m/s
Car D 100 m/s 99 m/s 98 m/s 97 m/s 96 m/s 95 m/s

 

 

 

 

 

 

 

2 Ways to Have
 Zero Acceleration

 

 

a) Remain at Rest

 

 

b) Constant Velocity  

 

 

 

1. Equation

 

 

a = ∆V/∆t  = (Vf - Vi)/t

 

 

 

 

Ex 1

 

Starting Velocity: 80 km/h West

 

Final Velocity: 110 km/h West

 

Acceleration:  1.6 m/s2

 

How long did it accelerate?

 

 

(Vf - Vi) = 30 km/h W

 

Convert to m/s2

 

30 km/hrx[1000m/km]x[1 h/3600 sec]

 

= 8 m/s

 

a = (Vf - Vi)/t

 

1.6 m/s2 = (8 m/s)/t

 

t = 5 sec

 

 

 

 

An object has an
acceleration of
-12 m/s2


Is it accelerating or decelerating?

 

 

Depends ....

 

 

If velocity is negative, accelerating

ex) -100 m/s to -124 m/s in 2 sec

If velocity is +, decelerating

124 m/s to 100 m/s in 2 sec

 

Acceleration

V +,  A+

V-, A-

Deceleration

V+, A-

V-, A+

 

 



 

'Accelerating Backwards'

 

(Because the force required to slow an object
 always opposes the objects motion)

 

 

 

 

 

 

 

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