1.

A car acquires a velocity of 72 km h^(-1) In 10 s starting from rest. Calculate : (i) the acceleration, (ii) the average velocity, and (iii) the distance travelled in this time.

Answer»

Solution :Given INITIAL velocity U =0 Final velocity v= 72 KM `h^(-1)`
`= (72xx1000 m)/(60xx60s)= 20 m s^(-1)`
TIME taken t = 10 s
(i) Acceleration a = `(v-u)/(t)`
`=((20-0)m s^(-1))/(10 s)= 2 m s^(-2)`
(ii) Average velocity =
`= (0 +20)/(2) m s^(-1) = 10 m s^(-1)`
(iii) Distance travelled S = average velocity `xx` time
`= (10 m s^(-1)) xx (10 s)`
= 100 m
Alternative method :
Distance travelled S = `ut+ (1)/(2) at^(2)`
= `0 +(1)/(2) xx2 xx(10)^(2)= 100` m


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