NOTES p.13

Graphs for Objects Thrown Up

30

20

4 t(s)

Speed(ms-1)

2

30

20

-20

4 t(s)

velocity(ms-1)

2

30

4 t(s)2

acceleration(ms-2)

-10

1. What distance does the ball travel during the 4 s?2. What is the displacement of the ball after 4 s?3. What is the speed of the ball at 4 s?

4. What is the velocity of the ball at 4s?

Area = 40 m

Area = 20 - 20 = 0 m

20 m/s

-20 ms-1

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.

Distance travelled = area below a speed-time graph

Displacement = Area below a velocity-time graph with areas below the time axis being negative!

30

20

4 t(s)

Speed(ms-1)

2

30

20

-20

4 t(s)

velocity(ms-1)

2

30

4 t(s)2

acceleration(ms-2)

-10

Q5. The sense of the motion changes after 2 s, yet the acceleration graph is one continuous line. Explain why.

AnswerAcceleration, due to gravity, is 10 ms-2 (rounded here for simplicity) DOWNWARDS, for the whole journey.

Over to you, again – 1. Complete the “Bouncing Ball” Graphs handout.2. Q. 29 - 32 from the Mechanics and Properties of Matter problems.

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 downBC – bounce (in contact)CD – travelling up to maximum height

DE – travelling downwards and speeding up

EF – second bounce

Answers to Q. 27 – 32

27.

28.

29.

30.

31.

32.

velocity (ms-1)

time(s)0 5 10

10

30

acceleration (ms-2) time(s)-10

2 103 405

-0.5