1. NOTES p.13
Balls in the Air!

2. Graphs for Objects Thrown Up
Try to draw graphs of speed, velocity and acceleration against time for a ball thrown vertically upwards at 20ms-1 and taking 4 s to land. 3 4
t(s) 2
acceleration
(ms-2)
-10 3 20 4
t(s)
Speed
(ms-1) 2 3 20
-20 4
t(s)
velocity
(ms-1) 2
What distance does the ball travel
during the 4 s?
What is the displacement of the ball
after 4 s?
What is the speed of the ball at 4 s?
What is the velocity of the ball at 4s?
Area = 40 m
Area = = 0 m
20 m/s
-20 ms-1

3. Distance travelled = area below a speed-time graph
Displacement = Area below a velocity-time graph with areas below the time axis being negative!

4. Acceleration, due to gravity, is 10 ms-2 20
Speed
(ms-1)
t(s) 2 3 4
t(s) 2 3 4
-10 20
velocity
(ms-1)
Q5. The sense of the motion changes after 2 s, yet the acceleration graph is one continuous line. Explain why.
t(s) 2 3 4
Answer
Acceleration, due to gravity, is 10 ms-2
(rounded here for simplicity) DOWNWARDS, for the whole journey.
-20

5. AB – ball travelling down BC – bounce (in contact)
Over to you – Draw the velocity-time graph of a ball that is released, drops and bounces twice. In this case take downwards as –ve and upwards as +ve. (Numerical axes are not required and assume no energy is lost due to negligible contact time with ground)
t(s)
velocity
(ms-1) A B C D E F
AB – ball travelling down
BC – bounce (in contact)
CD – travelling up to maximum
height
DE – travelling downwards and
speeding up
EF – second bounce
Over to you, again –
1. Complete the “Bouncing Ball” Graphs handout.
2. Q from the Mechanics and Properties of Matter problems.

6. Answers to Q. 27 – 32 29. velocity (ms-1) time(s) 5 10 30 55 10 30 5
acceleration (ms-2)
-0.5 2 3 4 10
time(s)
-10