Motion Flashcards
Units for distance
Metres m
Speed
Metres per second ms-1
Acceleration
Metres per second squared ms-2
If an object moves 100 metres in 12 seconds, what is it’s speed?
100m = d
12s = t
v = change in d/ change in t
v = 100/12
v = 8.33ms-1
An object starts from rest (0ms-1) and accelerates for 8 seconds, up to a speed of 20ms-1. What is it’s average acceleration?
8s = t
Change in v = final v - initial v = 20 - 0 = 20
a = change in v / change in t
a = 20/8
a = 2.5 ms-1
A turtle moves at a constant speed of 0.12ms-1 for 45 seconds. What distance does it cover?
0.12ms-1 = v
45s = t
v = change in d / change in t so
change in d = v x change in t
Change in d = 0.12 x 45
Change in d = 5.4m
An e-scooter has a starting speed of 1ms-1 and then accelerates at 2ms-2 for four seconds. What is it’s final speed?
2ms-1 = a
4s = t
1ms-1 = initial velocity
a = change in v / change in t so
change in v = a x change in t
change in v = 2 x 4
change in v = 8ms-1
So final speed = initial velocity + new velocity
1 + 8 = 9ms-1
What is constant speed?
When the speed is not changing
What is the difference between instantaneous speed and average speed?
Instantaneous speed is your speed at any particular second in time.
Average speed is found by taking the total distance you travelled and the total time it took.
What is the formula for calculating acceleration?
a = change in v / change in t (or rise/run)
How do you calculate change in v?
Change in v = final v - initial v
How do you calculate average speed?
v = change in d / change in t
How do you find the distance travelled from a speed-time graph?
Distance covered = area under graph
Area of rectangle = base x height
Distance = base x height
Or
Distance covered = area under graph
Area of triangle = 1/2 x base x height
Distance = 1/2 x base x height
