Projectile on an Upward Inclined Plane A projectile is launched with initial speed u at an angle θ to the horizontal onto an upward inclined plane of angle β (β > 0). What is the range R measured along the plane?

Introduction / Context:
Range on an inclined plane is a classic extension of projectile motion. Instead of measuring horizontal range, we measure distance along a plane inclined at angle β to the horizontal. The result depends on both the launch angle θ and the slope β.

Given Data / Assumptions:

• Initial speed u, launch angle θ to the horizontal.
• Inclined plane angle β (upward), no air resistance.
• Acceleration due to gravity g acts vertically downward.

Concept / Approach:
Resolve motion into components parallel and perpendicular to the incline or start from horizontal/vertical equations and impose the plane-impact condition y = x tan β at the point of contact. Algebra then gives range measured along the plane surface.

Step-by-Step Solution:

Verification / Alternative check:
For β = 0 (horizontal ground), formula reduces to R = (u^2 * sin 2θ) / g, which is the standard horizontal range, confirming correctness.

Why Other Options Are Wrong:
Using sin(θ + β) gives a larger angle and incorrect range sign for typical θ; the standard flat-ground result (option c) ignores the slope; the cos β factors in option d are not consistent with the plane geometry.

Common Pitfalls:
Forgetting to convert horizontal distance to along-plane distance (divide by cos β), mixing θ ± β signs, and algebraic slips solving the impact condition.

Final Answer:
R = (2 * u^2 * cos θ * sin(θ - β)) / (g * cos^2 β).