Question

For a projectile, the physical quantities which remain constant are:

• A. vertical component of velocity and kinetic energy.
• B. potential energy and kinetic energy.
• C. acceleration and horizontal component of velocity
• D. potential energy and acceleration.

Answer 1

The correct option is C acceleration and horizontal component of velocity

$\text{Step 1: Variable Quantities}$

$\text{[Ref. Fig.]}$

Here speed is changing at every instant, and height is also changing during motion.

Kinetic Energy $=\frac{1}{2}m{v}^2$

Potential Energy $=mgh$

$v$ and $h$ are changing so kinetic and potential energy will change.

$\text{Step 2: Constant Quantities}$

In $x$ direction there is no acceleration $\left(a_x\right)$ so horizontal component of velocity will not change (constant).

In $y$ direction acceleration is constant i.e. $g$. Therefore total acceleration is also constant.

Hence option $C$ is correct.