Question

A body of mass 2 kg, initially at rest, is moved by 3 m along the horizontal by a force of 10 N acting at an angle of $60^?$ with the horizontal. The kinetic energy gained by the body is

• A. $15\,J$
• B. $20\,J$
• C. $25\,J$
• D. $30\,J$

Answer 1

Answer: (A)

$15\,J$

Answer 2

Component of force along the direction of displacement $= F \,cos? = 10 ? cos60^? = 5 \,N$ Therefore, acceleration is $a=\frac{5\,N}{2\,kg}=2.5\,m\,s^{-2}$ As $\upsilon^{2}-u^{2}=2as$ or $\upsilon^{2}=2as\,\left(\because u=0\right)$ $\therefore K.E=\frac{1}{2}m\upsilon^{2}=mas=2\times2.5\times3=15\,J$