Question

On an object of mass 1kg moving along x-axis with constant speed 8m/s,a constant force 2N is applied in positive y-direction. Find its speed after 4 seconds.

Answer 1

The component of the velocity of the object along the y-direction undergoes an acceleration $a=\frac{F}{m} =\frac{2}{1}=2$.

The y-component of the velocity after 4 seconds is

$v_y=u_y+a_yt\\ v_y=0+2(4)\\ v_y=8 \;m/s$

The x-component of the velocity remains constant at

$v_x=8 \;m/s$

The speed after 4 seconds is

$v=\sqrt{v_x^2+v_y^2}=\sqrt{8^2+8^2}=8\sqrt{2} \;m/s$