Question

The only force acting on a $2 \,kg$ body that is moving in $xy-$ plane has a magnitude of $5\, N$ . The body initially has a velocity of $4 \,m/s$ in the positive $x$ -direction. Some time later, the body has a velocity of $6 \,m/s$ in the positive $y-$ direction. The work done on the body by the $5 \,N$ force during this time is

• A. 20 J
• B. 40 J
• C. 50 J
• D. 72 J

Answer 1

Answer: (A)

20 J

Answer 2

The correct answer is A :$20J$
Given, $m = 22\, kg$ ,
$V_{1}=4 m /s$ and $V_{2}=6 m /s$ $F=5 N$
According to work-energy theorem,
$\int F_{net} dx=\Delta zkE=\left(KE\right)_{2}-\left(KE\right)_{1}$
$=\frac{1}{2}mv_{2}^{2}-\frac{1}{2}mv_{1}^{2}$
$=\left[\left(6\right)^{2}-\left(4\right)^{2}\right]\frac{2}{2}$ [putting values]
$=\left[36-16\right]=20 \,J$