The equation of motion of a car is $s = t^{2} - 2 t$ , where t is measured in hours and s in kilometers. When the distance travelled by the car is 15 km, the velocity of the car is

2 km/h

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4 km/h

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2 km/h

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8 km/h

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Solution

The correct option is D 8 km/h
Given equation $s = t^{2} - 2 t . . . . (i)$
and $\frac{d s}{d t}$ = velocity =2t-2 ....(ii)
Put s =15 in (i), we get $t^{2} - 2 t - 15 = 0$
or (t-5)(t+3)=0
$∴ t = 5$
Hence velocity of car =v=2(5)-2=8 km/h.

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The equation of motion of a car is s=t2−2t, where t is measured in hours and s in kilometers. When the distance travelled by the car is 15 km, the velocity of the car is

The correct option is D 8 km/h Given equation s=t2−2t....(i) and dsdt = velocity =2t-2 ....(ii) Put s =15 in (i), we get t2−2t−15=0 or (t-5)(t+3)=0 ∴t=5 Hence velocity of car =v=2(5)-2=8 km/h.

The equation of motion of a car is $s = t^{2} - 2 t$ , where t is measured in hours and s in kilometers. When the distance travelled by the car is 15 km, the velocity of the car is

The correct option is D 8 km/h
Given equation $s = t^{2} - 2 t . . . . (i)$
and $\frac{d s}{d t}$ = velocity =2t-2 ....(ii)
Put s =15 in (i), we get $t^{2} - 2 t - 15 = 0$
or (t-5)(t+3)=0
$∴ t = 5$
Hence velocity of car =v=2(5)-2=8 km/h.