Welcome back, students!
In today’s tutorial, we’ll be solving one of the most challenging physics questions on projectile motion — specifically focused on how maximum height relates to time of flight. This is one of the trickiest but most examinable topics in JEE Physics.
Let’s break it down step by step.
You can watch the full class in the video below:
Question: Comparing the Time of Flight of Two Balls
Problem Statement:
Two balls with the same mass and the same initial velocity are projected at different angles. The maximum height reached by the first ball is eight times higher than that of the second ball.
Let:
- T1T_1T1 = total flight time of the first ball
- T2T_2T2 = total flight time of the second ball
Find the ratio T1T2\frac{T_1}{T_2}T2T1
Step-by-Step Explanation:
We are told:
- Mass is the same
- Initial velocity is the same
- H1=8H2H_1 = 8H_2H1=8H2
Now, we know the formula for maximum height in projectile motion: H=u2sin2θ2gH = \frac{u^2 \sin^2 \theta}{2g}H=2gu2sin2θ
For the two balls, this becomes: u2sin2θ12g=8×u2sin2θ22g\frac{u^2 \sin^2 \theta_1}{2g} = 8 \times \frac{u^2 \sin^2 \theta_2}{2g}2gu2sin2θ1=8×2gu2sin2θ2
Cancel u2u^2u2 and 2g2g2g from both sides: sin2θ1=8sin2θ2\sin^2 \theta_1 = 8 \sin^2 \theta_2sin2θ1=8sin2θ2
Now Calculate Time of Flight
Recall that time of flight is given by: T=2usinθgT = \frac{2u \sin \theta}{g}T=g2usinθ
So, T1=2usinθ1g,T2=2usinθ2gT_1 = \frac{2u \sin \theta_1}{g}, \quad T_2 = \frac{2u \sin \theta_2}{g}T1=g2usinθ1,T2=g2usinθ2
Now take the ratio: T1T2=sinθ1sinθ2\frac{T_1}{T_2} = \frac{\sin \theta_1}{\sin \theta_2}T2T1=sinθ2sinθ1
From the previous result: sin2θ1=8sin2θ2⇒sinθ1sinθ2=8=22\sin^2 \theta_1 = 8 \sin^2 \theta_2 \Rightarrow \frac{\sin \theta_1}{\sin \theta_2} = \sqrt{8} = 2\sqrt{2}sin2θ1=8sin2θ2⇒sinθ2sinθ1=8=22
Final Answer: T1T2=22\frac{T_1}{T_2} = \boxed{2\sqrt{2}}T2T1=22
Watch more educational videos and past questions: https://youtube.com/@allcbts
Why This Question Matters for JEE
This problem touches on several high-yield physics concepts:
- Projectile motion
- Time of flight & maximum height formulas
- Trigonometric identities
- Ratio simplification
These are all frequently tested in JEE Main and Advanced Physics exams.
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Master JEE Physics with this step-by-step solution to a projectile motion question. Learn how to relate maximum height to time of flight — a key concept in JEE 2025 Physics.
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JEE 2025 Physics, projectile motion JEE, time of flight formula, JEE past questions physics, maximum height projectile, trigonometry in motion, jee advanced problems