Question

A car accelerates from $10m{s}^{–1}to20m{s}^{–1}$. If the mass of the car is 500 kg, the work done is

• A. 75kJ
• B. 80kJ
• C. 85 kJ
• D. 60 kJ

Answer 1

The correct option is A 75kJ

Initial velocity, $u=10m{s}^{–1}\text{Final velocity, v}=20m{s}^{–1}\text{Mass, m}=500kg\text{Using Work-energy theorem:}\text{Work done = Change in kinetic energy}=(K.E.{)}_f-(K.E{)}_i\Rightarrow W=\frac{1}{2}m{v}^2-\frac{1}{2}m{u}^{2}W=\frac{1}{2}m{v}^2-u^2)W=\frac{1}{2}\times 500[(20{)}^2-(10{)}^2]W=\frac{1}{2}\times 500(400-100)=250\times 300=75000JW=75kJ$

Hence, the correct answer is option (a).