CHAPTER 6. MOTIONIN TWO DIMENSIONS 6.2
x [m]
t [s]
0 0,5 1,0 1,5 2,0 2,5
0
20
21,2
Step 6 : Graph of velocity vs. time
The ball starts off with avelocity of +4,9 m·s−^1 at t = 0 s, it then
reaches a velocity of 0 m·s−^1 at t = 0,5 s. It stops andfalls back to
the Earth. At t = 1,0s (i.e. after a further 0,5s) it has a velocity of
-4,9 m·s−^1. This is the same as theinitial upwards velocitybut it
is downwards. It carrieson at constant acceleration until t = 2,58
s. In other words, the velocity graph will be astraight line. The
final velocity of the ballcan be calculated as follows:
vf = vi+ gt
= 0 + (− 9 ,8)(2, 08.. .)
=− 20 , 396... m· s−^1
�
�
� t(s)
v( m· s−^1 )
4 , 9 �
− 4 , 9
− 20 , 40
0 , 5
1 , 0 2 ,^58
Step 7 : Graph of a vs t
We chose upwards to be positive. The acceleration of the ball is
downward. g =− 9 .8 m· s−^2. Because the acceleration is con-
stant throughout the motion, the graph looks like this:
