Can you calculate average speed?

Classical Mechanics Level 5

$S_{1}, S_{2}$ & $S_{3}$ are the different sizes of windows 1, 2 & 3 respectively, placed in a vertical plane. A particle is thrown up in that vertical plane. Average speed of the particle passing the windows may be equal if:

(Assume that the speed of the particle is sufficient so that it crosses all the windows.)

Try more from my set Classical Mechanics Problems .

None of these

S_{1}<S_{2}<S_{3}

S_{1}=S_{2}=S_{3}

S_{1}<S_{3}<S_{2}

S_{1}>S_{2}>S_{3}

1 solution

Purushottam Abhisheikh
Feb 3, 2015

When a particle is moving in uniform acceleration the average speed of particle between two points can be written as $\frac{V_{i} + V_{f}}{2}$ where $V_{i}$ & $V_{f}$ are the speed of particle at initial & final position respectively.

Since $V_{i} + V_{f}$ can never be equal whatever be the length of windows $S_{1}, S_{2}$ & $S_{3}$ , so average speed of particle can never be equal for any length of $S_{1}, S_{2}$ & $S_{3}$ .

The average speed between bottom point and top point of window S1, S2 & S3 will be different. In S1 average speed will be highest. So correct answer will be Si should be wider than S2 and S2 wider than S3

Ankur Guha - 5 years, 9 months ago

Have you done it Mathematically?

Purushottam Abhisheikh - 5 years, 9 months ago

Yes s1>s2>s3 how they got none of these

Tarun B - 4 years, 2 months ago

See for $S_{1}$ , if initial and final velocity be ${V_{i}}_{1}$ and ${V_{f}}_{1}$ respectively, the average velocity will be $\frac{{V_{i}}_{1}+{V_{f}}_{1}}{2}$ , similarly for $S_2$ it will be $\frac{{V_{i}}_{2}+{V_{f}}_{2}}{2}$ and for $S_3$ it will be $\frac{{V_{i}}_{3}+{V_{f}}_{3}}{2}$ . And we all know that $|{V_{i}}_{1}| > |{V_{f}}_{1}| > |{V_{i}}_{2}| > |{V_{f}}_{2}| > |{V_{i}}_{3}| > |{V_{f}}_{3}|$ . Now you can check yourself which will be the correct answer.

Purushottam Abhisheikh - 4 years, 1 month ago

Can you calculate average speed?

1 solution

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