Motion in a Straight Line - Result Question 43

45. If a ball is thrown vertically upwards with a velocity of $40 m / s$, then velocity of the ball after two seconds will be ( $g=10 m / s^{2}$ )

[1996]

(a) $15 m / s$

(b) $20 m / s$

(c) $25 m / s$

(d) $28 m / s$

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Answer:

Correct Answer: 45. (b)

Solution:

  1. (b) Initial velocity $(u)=40 m / s$ Acceleration $a=-g m / s^{2}=-10 m / s^{2}$

Time $=2$ seconds

By Ist equation of motion,

$v=u+a t$

$v=40-10(2)=20 m / s$