Question

The potential energy of a system is represented in the first figure. The force acting on the system will be represented by

• A.
• B.
• C.
• D.

Answer 1

The correct option is C

$F=-\frac{dU}{dx}$
Upto point $a$, the slope of $U\left(x\right)$ vs $x$ curve is positive.
Hence $\frac{dU}{dx}$ is positive and force is a constant negative value.
After point $a$ the $U\left(x\right)$ curve becomes constant and the force becomes zero.