A car of mass $$\(1250 \mathrm{~kg}\)$$ is moving on a straight road. On a horizontal section of the road, the car has a constant speed of $$\(32 \mathrm{~m} \mathrm{~s}^{-1}\)$$ and there is a constant force of $$\(750 \mathrm{~N}\)$$ resisting the motion. Given that this power is suddenly decreased by $$\(8 \mathrm{~kW}\)$$, find the instantaneous deceleration of the car. ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................
Exam No：9709_s20_qp_42 Year：2020 Question No：5(a)(ii)
Answer:
\(16000=D F \times 32\)
\(D F=500\)
\(500-750=1250 \times a\)
\(a=[-] 0.2\)
\(D F=500\)
\(500-750=1250 \times a\)
\(a=[-] 0.2\)
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
Solution:
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