Question

Work is said to be NOT done when an object moves

• A. At an angle of ${90}^o$ to the direction of the force
• B. At an angle opposite to the direction of the force
• C. At any angle to the direction of the force
• D. Along the direction of the force

Answer 1

The correct option is A At an angle of ${90}^o$ to the direction of the force

Work is not said to be done when an object moves at 90 degree to the direction of the force. Because work done = F.x Cos$\theta$ = F.x Cos90 = 0 (Since Cos90 degree is zero). Hence when force and displacement angle are perpendicular to each other no work is said to be done.