Question

A small object moves counter clockwise along the circular path whose centre is at the origin as shown in figure. As it moves along the path, its net acceleration vector continuously points towards point $\text{S}$. Then the object

• A. Speeds up as it moves from $\text{A}$ to $\text{C}$ via $\text{B}$.
• B. Slows down as it moves from $\text{A}$ to $\text{C}$ via $\text{B}$.
• C. Slows down as it moves from $\text{C}$ to $\text{A}$ via $\text{D}$.
• D. Speeds up as it moves from $\text{C}$ to $\text{A}$ via $\text{D}$.

Answer 1

Answer: (A), (C)

The correct options are
A Speeds up as it moves from $\text{A}$ to $\text{C}$ via $\text{B}$.
C Slows down as it moves from $\text{C}$ to $\text{A}$ via $\text{D}$.


As the object moves from $\text{A}$ to $\text{C}$ via $\text{B}$, the angle between net acceleration vector $\left(a\right)$ and velocity vector $\left(v^{\prime }\right)$ is acute $(\theta <{90}^{\circ })$, hence object speeds up.
($\because$ component of net acceleration will be parallel to direction of $v^{\prime }$)

As the object moves from $\text{C}$ to $\text{A}$ via $\text{D}$, the angle between net acceleration vector $\left(a\right)$ and velocity vector $\left(v\right)$ is obtuse $(\theta >{90}^{\circ })$, hence object will slow down.
($\because$ component of net acceleration will be anti-parallel to direction of $v^{\prime }$)