Question #92775

1 Answer
Jan 13, 2017

37.4ms^-1, rounded to one decimal place.

Explanation:

It is supposed the bullet is fired from the ground level. When the bullet is fired it has velocities V_x = 30ms^-1 and V_y = 40ms^-1 in the x and y directions respectively. Ignoring the effect of air resistance there is no change in the velocity in x direction.

The motion in the y direction is governed by motion under the influence of acceleration due to gravity =9.81ms^-2.
Kinematic equation is

v=u+g t
where v is final velocity after time t and u is initial velocity.

Inserting given values we get, remember that direction of acceleration due to gravity is along -y direction
V_(y1.8)=40-9.81xx 1.8=22.342ms^-1

Modulus of velocity of bullet at t=1.8s is given by the expression
|V_(1.8)|=sqrt(V_(y1.8)^2+V_x^2)
=>|V_(1.8)|=sqrt((22.342)^2+(30)^2)=37.4ms^-1, rounded to one decimal place.