A car is moving with uniform acceleration. It covers 200 m in 2 sec and 220 m

⇦

⇨

A car is moving with uniform acceleration. It covers 200 m in 2 sec and 220 m in next 4 sec. The velocity of car at the end of 7th second from start is

Options

(a) 1 m/s
(b) 0.1 m/s
(c) 10 m/s
(d) 20 m/s

Correct Answer:

10 m/s

Explanation:

For first 2 second
S = 2u +1/2α (2)²
200 = 2u + 2α
or u + α = 100 …(i)
For first 2 + 4 = 6 second
S = 200 + 220 = 420 m
420 = 6u + 36/2 α
420 = 6u + 18α ⇒ 420 = 6(u + 3α)
u + 3α = 420/6 = 70 …(ii)
Solving equation (i) and (ii)
α = -15 m/sec²
This is the retardation.
Using these formula V=ut+1/2 αt²
200 = u+1/2 (-15)(2)²
u = 115
Hence velocity after 7 second is
V = u+αt
= 115 + (–15) x 7
= 10 m/sec.

Related Questions:

1. The angle between the vectors (i+j) and (j+k) is
2. A wheel has moment of inertia 5 x 10⁻³ kgm² and is making 20 revolutions per sec
3. If Q, E and W denote respectively the heat added, change in internal energy
4. The threshold frequency for a certain photosensitive metal is ν₀. When it is illuminated
5. A sound absorber attenuates the sound level by 20 dB. The intensity decreases

Topics: Motion in Straight Line (93)
Subject: Physics (2479)

---

Important MCQs Based on Medical Entrance Examinations To Improve Your NEET Score

18000+ students are using NEETLab to improve their score. What about you?

Solve Previous Year MCQs, Mock Tests, Topicwise Practice Tests, Identify Weak Topics, Formula Flash cards and much more is available in NEETLab Android App to improve your NEET score.

---

Share this page with your friends