an object starting from rest travels 20 metres in the first 2 seconds,and 100 metres in the next 10 seconds . what will be the velocity after 7 seconds from start.
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Given :-
An object starting from rest travels 20 metres in the first 2 seconds,and 100 metres in the next 10 seconds .
To Find :-
Velocity after 7 sec
Solution :-
We know that
s = ut + 1/2 × at²
20 = (0)(2) + 1/2 × a × (2)²
20 = 0 + 1/2 × a × 4
20 = 2a
20/2 = a
10 = a
Now
v² = u² + 2as
v² = (0)² + 2(10)(20)
v² = 0 + 20 × 20
v² = 400
v = √400
v = 20 m/s
Now
After 2 seconds
v = u
s = ut + 1/2 at²
100 = (20)(10) + 1/2 × a × (10)²
100 = 200 + 1/2 × a × 100
100 = 200 + 50a
100 - 200 = 50a
-100 = 50a
-100/50 = a
-2 = a
Now
v = u + at
v = 20 + (-2)(7)
v = 20 + (-14)
v = 20 - 14
v = 6 m/s
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