Question

15. A car starting from rest accelerates uniformly along a straight line. If it attains a velocity
of 120 kmph in 12s, what is the acceleration of the car in m/s??
​

Answer 1

Answer:

Correct option is

B

5 km

Here, u=0,v=20km/h,t=30min=0.5h

Putting these values in v=u+at

20=0+a∗0.5

We get, a=40km/h

2

Putting the values in S=ut+

2

1

at

2

S=0∗0.5+

2

1

∗40∗0.5

2

S=5km

Answer 2

Explanation:

Speed after 25 s = 180 km/h = 180 ×(5/18) m/s = 50 m/s

From equation v = u + a t , we get acceleration. where v is final speed, u is initial speed which is zero because

the car strats from rest, a is acceleration and t is time taken to attain the final speed.

hence v = a t or 50 = a×25 or acceleration a = 50/25 = 2 m/s2 .

distance travelled, S = (1/2)a t2 = (1/2)×2×25×25 = 625 m