Question

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

Answer 1

Given,

$Mass=1kg$

$speed=8m/s$

$f=2N$

$t=4s$

So,

$V_x=8m/s$ ( velocity in x - axis )

$F_y=2N$ ( force act on body in y-direction

We know,

$F=ma$

$2=1\times a$

$a=2m/s²$ In y- direction,

Now, By using vector kinematics formula

$V=U+at$

Here,

$U=8i,a=2j,t=4$

$V=8i+2j\times 4=8i+8j$

Thus, final velocity = 8i + 8j

Again,

We know, speed $=|velocity|$

$speed=\sqrt{(8^2+8^2)}=\sqrt{(2\times 8^2)}$

$=8\sqrt{2}m/s$