Projectile motion on inclined planes: Compare the range on a downward slope versus an upward slope for identical launch parameters. Conditions: Same initial speed (u) and same launch angle (α) with respect to the horizontal; magnitude of plane inclination (|β|) is the same in both cases. Choose the correct comparative statement about the range measured along the plane.
Mechanical Engineering
Engineering Mechanics
Difficulty: Easy
Choose an option
Answer
Correct Answer: Greater than
Explanation
Given data
- Same initial speed u and launch angle α for both cases.
- Same magnitude of plane inclination |β| (one case upward, the other downward).
Concept/Approach For a projectile on an inclined plane, the range along the plane is R(β) = (2u2 cosα · sin(α − β)) / (g cos2β) where β is taken positive for an upward slope and negative for a downward slope.
Step-by-step reasoning Upward plane: Rup ∝ sin(α − β). Downward plane: Rdown ∝ sin(α − (−β)) = sin(α + β). For 0 < β < α < 90°, we have sin(α + β) > sin(α − β). ⇒ Rdown > Rup.
Common pitfall Do not compare horizontal ranges; the comparison is for range measured along the plane.
Final Answer Greater than