A car of mass $$$1800 \mathrm{~kg}$$$ is travelling along a straight horizontal road. The power of the car's engine is constant. There is a constant resistance to motion of $$$650 \mathrm{~N}$$$. Find the power of the car's engine, given that the car's acceleration is $$$0.5 \mathrm{~m} \mathrm{~s}^{-2}$$$ when its speed is $$$20 \mathrm{~m} \mathrm{~s}^{-1}$$$. ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................ ........................................................................................................................................................

Mathematics

IGCSE&ALevel

CAIE

Exam No：9709_w20_qp_42 Year：2020 Question No：2(a)

Answer:

$\mathrm{DF}-650=1800 \times 0.5 \quad[\mathrm{DF}=1550]$
$\frac{P}{20}-650=1800 \times 0.5$
[Power $P=1550 \times 20=$ ] $31000 \mathrm{~W}$ or $31 \mathrm{~kW}$

Knowledge points:

4.5.4 use the definition of power as the rate at which a force does work, and use the relationship between power, force and velocity for a force acting in the direction of motion Including calculation of (average) power;P = Fv

4.5.5 solve problems involving, for example, the instantaneous acceleration of a car moving on a hill

Answer:

Knowledge points:

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