urgent urgent... A motorcycle can be driven maximum with an acceleration of 6 m/s2, whereas its brakes can be applied to give maximum retardation of 12 m/s2. The minimum time, in which it can cover a distance of 800 metre, is
(1) 10 seconds (2) 20 seconds (3) 15 seconds (4) 40 seconds
Answers
Answer:
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Answer:
Given acceleration a= 5m/s
2
and maximum retardation =10 m/s
2
and distance between A and B= 1.5 km= 1500 m
We know acceleration a=
t
v−u
considering u= 0 m/s as initially the motorcycle is at rest.
So v=5t., where t is the time taken to accelerate.------(A)
As T is the total time than time taken for retardation by an amount of 10 m/s
2
be T-t.
From equation of motion we have retardation=
time
Finalvelocity−initial
In case of retardation or deceleration final velocity will be 0 as the motorcycle will come to rest.
So −v=−10(T−t)-------(B)
Putting the value of A in B we get
−5t=−10T+10t
T=
2
3t
-------(C)
As the total distance covered by the motorcycle in T seconds=1500 m,
thus
2
1
vT=1500
vT=3000
As earlier found v=5t and T=
2
3t
5t
2
3t
=3000
t
2
=400
t=20s
we know T=
2
3t
T=30s