Question

Draw speed time graph for a ball thrown upward with speed 20m/s from 0 to 4s.Also calculate the distance travelled by ball in the whole journey.

Answer 1

Speed-Time graph:

Velocity at any $\rm ins{t}ant$:

$\rm \: v = u + at$

$\rm \implies \: v = 20 - gt$

$\rm \implies \: v = - gt + 20$

• But since we are drawing speed instead of velocity in graph, we will plot positive values always.

$\rm \implies \: s = | - gt + 20 |$

• Now, at t = 2 sec, speed = 0 m/s.

• At t = 4 sec, speed = 20 m/s.

NOW , REFER TO GRAPH !!

Let distance travelled be d :

$\rm \: d = area \: under \: s - t \: graph$

$\rm \implies\: d = 2 \times ( \dfrac{1}{2} \times 2 \times 20)$

$\rm \implies\: d = 40 \: m$

So, distance travelled is 40 metres.