Assertion (A) The velocity of a projectile at a point on its trajectory is equal to the slope at that point. Reason (R) The velocity vector at a point always along the tangent to the trajectory at that point.

• A

  Both A and R are true and R is the correct explanation of A
• B

  Both A and R are true but R is not the correct explanation of A
• C

  A is true but R is false
• Correct answer
  D

  A is false but R is true

Solution

Trajectory of a projectice is of form $$ \begin{aligned} & y=f(x)=x \tan \theta-\frac{g x^2}{2 u^2 \cos ^2 \theta} \\ & \therefore \frac{d y}{d x}=\text { slope }=\frac{d y / d t}{d x / d t}=\frac{v_y}{v_x} \end{aligned} $$ So, Assertion (A) is incorrect. Also, velocity of a projectile is always along tangent to the trajectory (shown)
Hence, reason $(R)$ is correct.

Hence, the correct answer is option: 'D'.