Question

A dragster, starting from rest, accelerates at 28 m/s/s for 4.5 s. Then the parachute comes out and it slows to 46 m/s in 10 s. Determine its acceleration in those 10 s when the parachute is deployed. Show your working.

Answer 1

First find acceleration before opening

parachute

• Initial velocity=u=0m/s
• Acceleration=28m/s^2
• Time=t=4.5s

$\\ \bull\tt\dashrightarrow v=u+at$

$\\ \bull\tt\dashrightarrow v=0+28(4.5)$

$\\ \bull\tt\dashrightarrow v=126m/s$

Now

After opening the parachute the Final velocity calculated above would become initial velocity

• u=126m/s
• v=46m/s
• Time=10s

$\\ \bull\tt\dashrightarrow Acceleration=\dfrac{v-u}{t}$

$\\ \bull\tt\dashrightarrow Acceleration=\dfrac{46-126}{10}$

$\\ \bull\tt\dashrightarrow Acceleration=\dfrac{-80}{10}$

$\\ \bull\tt\dashrightarrow Acceleration=-8m/s^2$