Question

What braking force is needed to bring a $2200ki\log ram$ car going $18meters$ per second to rest in $6.0seconds$ ?

• A. $6600\mathrm{N}$
• B. $6500\mathrm{N}$
• C. $6000\mathrm{N}$
• D. $6200\mathrm{N}$

Answer 1

The correct option is A

$6600\mathrm{N}$

Step 1: Given data

Mass of car, $m=2200\mathrm{kg}$
The initial velocity of the car, $u=18\mathrm{m}/\mathrm{s}$
The final velocity of the car, $v=0$
Time, $t=6\mathrm{s}$

Step 2: Calculations.
Retardation of the car, $a=\frac{v-u}{t}$
$a=\frac{0-18}{6}=-3\mathrm{m}/{\mathrm{s}}^2$
Force is given by
$F=m\times a$
$F=2200\times (-3)=-6600N$.[-ve sign indicates retarding force]