Question

Calculate the work required to be done to stop a car of 1500 kg moving at a velocity of $60km{h}^{-1}$

• A. $-208333J$
• B. $208333J$
• C. $-209333J$
• D. $-207333J$

Answer 1

The correct option is A $-208333J$

Given, $massofcar,m=1500kg$;

$velocityofcar,v=60km{h}^{-1}=60\times \frac{5}{18}=\frac{50}{3}m/s$

$Workdone=Changeinkineticenergyofthecar$

or $W=\frac{1}{2}m{v}^2-\frac{1}{2}m{u}^2=\frac{1}{2}m(v^2-u^2)$

or $W=\frac{1}{2}\left(1500\right)\left[\right(0{)}^2-\left(50/3{)}^2\right]$

or $W=\frac{1}{2}\times 1500\times \frac{2500}{9}=-208333J$