Question

A truck weighing $1000kgf$ changes its speed from $36km{h}^{-1}$ to $72km{h}^{-1}$ in $2$ minutes.$(g=10m{s}^{-2})$. Calculate the work done by the engine

• A. $1.5\times {10}^{4}J$
• B. $1\times {10}^{5}J$
• C. $7.2\times {10}^{5}J$
• D. $0J$

Answer 1

The correct option is A $1.5\times {10}^{4}J$

We know that 1 Km/h = 5/18 m/sec.
That is 36 Km/h = 10 m/sec and 72 Km/h = 20 m/sec.
$K.E=0.5m{v}^2$
For work done by the engine we need to take the difference i.e
$W=0.5\times 100\times ({20}^2-{10}^2)J$
$W=1.5\times {10}^{4}J$.