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**A body covers 200 cm in the first 2 seconds and 220 cm in the next 4 seconds. The velocity of the body at the end of the 7th second is **

### Options

(a) 10 cm/s

(b) 20 cm/s

(c) 5 cm/s

(d) 30 cm/s

### Correct Answer:

10 cm/s

### Explanation:

Let u and a be the initial velocity and uniform acceleration of the body.

Using kinematic equation, S = ut + (1/2) at²

.·. 200 = u × 2 + (1/2) a × 2²

⇒ 100 = u + a ——-(i)

Also 420 = 6u + (1/2) a × 6²

⇒ 70 = u + 3a ——-(ii)

Solving equation (i) and (ii), we get u = 115 cms⁻¹, a = -15 cms⁻²

Using equation, v = u + at .·. v = 115 + (-15) × 7 = 10 cms⁻¹

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Topics: Motion in Straight Line
(93)

Subject: Physics
(2479)

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