1. What’s the equation for average speed?
v=d
t
2. A trolley has an average speed of 0.5 ms-1.
How far will it travel in 3 minutes?
d = ?
t = 3 minutes
= 3 x 60 s
= 180 s
v = 0.5
ms-1
d=v xt
= 0.5 x 180
= 90 m
3. What words mean the speed at a moment in time?
Instantaneous speed
4. How would you measure this speed?
Equipment: trolley with card on top, light gate, timer, ruler
Measurements: Length of card (with ruler), time to through
light gate
Calculations: v = d
t
where d is length of card and
t is time on timer
5. What is meant by a scalar quantity?
A scalar is defined by size (magnitude) only
Give 2 examples.
2 from - time, energy, power, distance, mass, speed
6. What is meant by a vector quantity?
A vector is defined by size (magnitude) AND direction
Give 2 examples.
2 from -force, displacement, velocity, acceleration
7. A jogger ran 30m East then 40m North. This took her
25s. Calculate
a) her distance travelled d = 30 + 40 = 70 m
b) her displacement
displacement2= 302 + 402 =
90 + 160
250
So displacement = a250
= 50 m
40m
y
30m
Direction: tan y = Opp
Adj
= 40
30
y = tan-1 (40/30)
y = 53 o
So 53 o North of East
Or 037 ( 37o from North)
c) her average speed
d = 70 m
t = 25 s
v = ?
v =d
t
= 70
25
= 90 m/s 0r ms-1
d) her average velocity
d = 50 m
t = 25 s
v = ?
v =d
t
= 70
25
= 90 m/s 0r ms-1 at 037
8. A plane flies at 100 kmh-1, West.
A wind is blowing to the South at 20 kmh-1.
Calculate the resultant velocity of the plane?
100 kmh-1
y
20 kmh-1
x
x2= 1002 + 202
= 10000 + 400
= 100400
So displacement = a100400
= 103 kmh-1
Direction: tan y = Opp
Adj
= 20
100
y = tan-1 (20/100)
y = 11 o
So 11 o South of West
Or 259 ( 259o from North)
9. Look at the following velocity – time graph.
6
velocity
(ms-1)
0
4
8
time (s)
a) Calculate the acceleration during the first 4 seconds.
b) Calculate the displacement after 8 seconds.
a) a =
v=
u=
t=
?
6 ms-1
0 ms-1
4s
a = (v-u)
t
= (6-0)
4
= 1.5 ms -2
6
velocity
(ms-1)
Area 2
Area 1
0
4
8
time (s)
b) Calculate the displacement after 8 seconds.
Displacement = area under the graph
= area 1 + area 2
= 1 base x height + length x breadth
2
= (1 x 4 x 6) + (4 x 6)
2
= 12 + 24
= 36m
10.
A car accelerates at 2 ms-2. If it starts from rest,
what will be its speed after 1 minute?
a) a =
v=
u=
t=
2 ms-2?
?
0 ms-1
60 s
v = u+at
= 0 + (2x60)
= 120 ms-1