Question

The displacement-time graph of a body acted upon by some forces is shown in figure. For this situation, match the entries of Column I with the entries of Column II.

Column I		Column II
i	For $O A$, the total work done by all forces together is	a	always positive
ii	For $O A$, the work done by few of the acting forces is	b	can be positive
iii	For $A B$, the work done by few of the acting forces is	c	zero or can be zero
iv	For $B C$, the work done by all forces together is	d	can be negative

• A. i $\rightarrow$ a; ii $\rightarrow$ b, c, d; iii $\rightarrow$ b, c, d; iv $\rightarrow$ c
• B. i $\rightarrow$ b; ii $\rightarrow$ c; iii $\rightarrow$ a; iv $\rightarrow$ c
• C. i $\rightarrow$ d; ii $\rightarrow$ c; iii $\rightarrow$ a; iv $\rightarrow$ a
• D. i $\rightarrow$ b; ii $\rightarrow$ c; iii $\rightarrow$ d; iv $\rightarrow$ a

Answer 1

Answer: (A)

In $O A$, velocity increases, hence $KE$ increases. So overall work done is positive. If a number of forces are acting on the body, then it is possible that some forces do positive work, some negative and some zero.
In $B C$, velocity is constant, hence there is no change in $KE$. So net work done by all the forces is zero.