Question

14. A particle is situated at x=+3 units at t=0, it starts moving from rest with a constant acceleration of 4m/s2. The position of the particle at t=3s is - (A) x = +21 units (B) x= +18 units (C) x=-21 units (D) None of these​

Answer 1

A +21 units

use s = ut+1/2at²

here

u = 0

t. = 3s

a = 4

putting values in equation

s = 0×3+(1/2)×(4)× 3²

= 18

but final position= 3+18= 21 units

Answer 2

Given info : A particle is situated at x = +3 units at t = 0 sec, it starts moving from rest with a constant acceleration of 4m/s².

To find : the position of the particle at t = 3sec is ...

solution : initial velocity of the particle, u = 0 m/s

acceleration of the particle, a = 4 m/s²

initial position of the particle, s₀ = 3  [ positive x - axis ]

time taken , t = 3 sec

using formula, $\bf{s=s_0+ut+\frac{1}{2}at^2}$

where s is the position of the particle at t = 3 sec.

s = 3 + 0 × 3 + $\frac{1}{2}$ × 4 × 3²

= 3 + 2 × 3²

= 21

therefore the position of the particle at t = 3 sec is x = 21 units. hence the correct choice is (C) x = 21 units.