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. A lift is moving down with acceleration a.A man in the lift drops a ball
2. Three particles A,B and C are thrown from the top of a tower with the same speed.
3. A bomb of mass 30 kg at rest exploded into two pieces of masses 18 kg
4. 4 point charges each +q is placed on the circumference of a circle
5. A particle with total energy E is moving in a potential energy region U(x)

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