1. Tardigrade
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  4. If a car at rest accelerates uniformly to a speed of 144 km/h in 20 s, it covers a distance of :

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Q. If a car at rest accelerates uniformly to a speed of 144 km/h in 20 s, it covers a distance of :

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Solution:

Key Idea: Distance covered will be according to 2nd equation of motion i. e., $ s=ut+\frac{1}{2}a{{t}^{2}} $ . Here, $ u=0,\,t=20s $ $ v=144km/h $ $ =144\times \frac{5}{18}m/s $ $ =40m/s $ From 1st equation of motion, $ v=u+at $ $ \Rightarrow $ $ a=\frac{v-u}{t}=\frac{40-0}{20}=2m/{{s}^{2}} $ Now, 2nd equation of motion, $ s=ut+\frac{1}{2}a{{t}^{2}} $ $ =0+\frac{1}{2}\times 2\times {{(20)}^{2}}=400m $ NOTE: If the car decelerates, the acceleration will be negative and is termed as retardation.