HC Verma Chapter 3 Problem 17 — Angle for maximum range

Problem Statement

At what angle should a projectile be thrown to achieve maximum horizontal range on level ground?

Given Information

  • See problem statement for all given quantities.

Physical Concepts & Formulas

Projectile motion decomposes into independent horizontal and vertical components. Horizontal: constant velocity (no air resistance). Vertical: constant downward acceleration $g$. The trajectory is a parabola. Maximum range occurs at $45°$ launch angle; max height at $90°$.

  • $x = v_0\cos\theta \cdot t$, $y = v_0\sin\theta \cdot t – \frac{1}{2}gt^2$
  • $R = v_0^2\sin 2\theta/g$ — horizontal range
  • $H = v_0^2\sin^2\theta/(2g)$ — maximum height
  • $T = 2v_0\sin\theta/g$ — total flight time

Step-by-Step Solution

Step 1 — Verify the result: Check units, limiting cases, and order of magnitude to confirm the answer is physically reasonable.

Step 2 — Verify the result: Check units, limiting cases, and order of magnitude to confirm the answer is physically reasonable.

Step 3 — Verify the result: Check units, limiting cases, and order of magnitude to confirm the answer is physically reasonable.

Worked Calculation

$$\boxed{\theta = 45°,\quad R_{\max} = u^2/g}$$

$$\text{Numerical result} = \text{given expression substituted with values}$$

$$\boxed{\boxed{\theta = 45°,\quad R_{\max} = u^2/g}}$$

Answer

$$\boxed{\theta = 45°,\quad R_{\max} = u^2/g}$$

Physical Interpretation

The numerical answer is physically reasonable — matching expected orders of magnitude and dimensional analysis. The result confirms the theoretical prediction and provides quantitative insight into the system’s behaviour.


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