Question

A car of mass 1250 kg experience a resistance of 750 N when it moves at 30ms^–1. If the engine can develop 30kW at this speed, the maximum acceleration that the engine can produce is

• A. $0.8ms^{- 2}$
• B. $0.2ms^{- 2}$
• C. $0.4ms^{- 1}$
• D. $0.5ms^{- 2}$

Answer 1

Answer: (B)

$0.2ms^{- 2}$

Answer 2

Power = Force × velocity = (Resistive force + Accelerating force) × velocity

⇒ $30 \times 10^{3} = (750 + ma) \times 30$

⇒ $ma = 1000 - 750$ ⇒ $a = \frac{250}{1250} = 0.2ms^{- 2}$.