Question

A particle of mass m moves with constant speed 8m/s,a constant force of 2n is applied in positive y-direction.Find its speed after 4 seconds.

Answer 1

Vx = 8 { velocity in x - axis )

Fy = 2N { force act on body in y-direction }

we know,

F = ma

2 = 1 × a

a = 2 m/s² In y - direction ,

now, use vector kinematics formula

V = U + at

here,

U = 8i

a = 2j

t = 4

V = 8i + 2j × 4 = 8i + 8j

hence, final velocity = 8i + 8j

we know, speed = | velocity|

speed = √(8² +8²) = √(2×8²)

= 2√8 m/s