Question

A plot of velocity versus time is shown in figure. A single force acts on the body. The correct statement is

• A. In moving from C to D, work done by the force on the body is positive
• B. In moving from B to C, work done by the force on the body is positive
• C. In moving from A to B , the body does negative work on the system
• D. In moving from O to A , work is done by the body and is negative

Answer 1

The correct option is B In moving from B to C, work done by the force on the body is positive

• As the area of a velocity - time graph represents the displacement of the system as:
  

$s=vt$ where s is displacement.

• The area is negative when the body moved from C to D since the area covered by CD line and t-axis in the fourth quadrant ,There fore:
  

Work =force$\times$ displacement

Work done is also negative.

• When the body moves from B to C,area covered is positive,So work done by force on the body is positive.
• From A to B ,displacement is again positive ,so work done by force on the body is positive.
  
• In moving from O to A,work done by force on the body is again positive.