Upload
amie-reynolds
View
223
Download
3
Embed Size (px)
Citation preview
Motion Graphs
1. Speed .
. )(
)()(
Time
DistanceSpeed m or cm/second
m or cm
seconds S
D
T
Examples using the Speed Formula (Showing full working):
1. The sprinter ran 100 metres in 10 seconds. What was his speed ?
Time
DistanceSpeed
s
m
10
100 sm /10
2. The porsche travelled at 40 m/s for 2 minutes. How far did it go ?
TimeSpeedDistance ssm 120/40 m4800
Nb VELOCITY (v)is simply speed in a given directionDISPLACEMENT (S) is the distance in a given direction
2. Acceleration
The acceleration of something tells us how quickly its speed is changing.We can say that acceleration is the amount ………..changes per …….…...speed second
)(
)()(
Time
SpeedinChangeonAccelerati metres/second 2
metres/second
secondsA
S
T
Time
SpeedinChangeonAccelerati
t
uv
1. The ferrari was travelling at 20 m/s behind a lorry. It pulled out to overtake and accelerated at 4 m/s2 for 2 seconds. What was its new speed ?
TimeonAcceleratispeedinChange ssm 2/4 2 sm /8
New Speed = Old Speed + Change in Speed = 20 m/s + 8 m/s = 28 m/s
or Where v = final velocity
u = initial velocity
4. Motion Represented on Graphs.
There are two types of motion graphs, and three types of motion. Best represented in a table.
Velocity/TimeDistance/Time
Stopped
Const’ Velocity
Const’ Accel’n
D
t
D
t
D
t
V
t
V
t
V
t
Gradient = Velocity Gradient = Accel’nArea = Distance
travelled
Question
Velocity Time Graph for parachutist.
150
15
15
50 100
V (m/s)
T (s)
A. What was his acceleration from 0 to 15 sec ?
T
VA
s
sm
15
/150
2/10 sm
B. What was happening at 50 seconds?
He had just opened his parachute and was decelerating.
C. Approximately how far did he fall altogether?
Area under graph 50 150 + 50 15 = 8250m
Distance time graphs ;Summary The gradient of a distance time
graph gives the velocity increasing gradient means object
is accelerating decreasing gradient means object
is decelerating zero gradient means object is
stationary
Velocity time graphs; Summary
The gradient of a velocity time graph gives the acceleration of an object
the area under a velocity time graph gives the total distance traveled
Increasing or decreasing gradient gives the rate at which the acceleration is increasing or decreasing
Zero gradient means the object is travelling at constant speed
Problems
1. Calculate the speed over OA AB and BC
2. Calculate (a)the acceleration over OA, AB and BC
(b) the total distance traveled in the 12 s
5, 0, 3.75m
5m/s2, 0, 3.75m/s2, 127.5m