Question

a car is travelling at 80km/h along a road . a child at 100m ahead . what must the car decelerated if the car stops just before child​

Answer 1

$\red{\bigstar}\underline{\underline{\textsf{\textbf{ Given :- }}}}$

• A car is travelling at 80km/h along a road .
• A child at 100m ahead .

$\red{\bigstar}\underline{\underline{\textsf{\textbf{ To Find :- }}}}$

• The deacceleration of car to stop the car just before child .

$\red{\bigstar}\underline{\underline{\textsf{\textbf{ Solution :- }}}}$

We need to find out the acceleration of the car so that it stops just before the child . Here we are given intial Velocity , distance and since the car is to be stopped the final velocity will be 0 . We can use the Third equation of motion as ,

• Also we need to convert the units into SI unit . The distance will be 100 m and the initial Velocity will be 22.22 m/s ≈ 80km/hr .

$\sf\dashrightarrow 2as = v^2- u^2 \\\\\\\sf\dashrightarrow 2 * a * 100 m = ( 0m/s)^2-(22.22 m/s)^2 \\\\\\\sf\dashrightarrow 200 a = - 493 .72 m/s^2 \\\\\\\sf\dashrightarrow a = \dfrac{-493.72}{200} m/s^2 \\\\\\\sf\dashrightarrow \underset{\blue{\sf Required\ Acceleration}}{\underbrace{\boxed{\pink{\frak{ Acceleration = -2.46 m/s^2}}}}}$