Projectile Motion (Initial Velocity)

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Homework Help Overview

The discussion revolves around determining the initial velocity of a ball kicked from point A to clear a wall at point B, focusing on projectile motion principles. The scenario involves a wall height of 4m and a horizontal distance of 20m from the launch point, with participants exploring various kinematic equations and concepts related to vertical and horizontal motion.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning, Problem interpretation

Approaches and Questions Raised

  • Participants discuss using trigonometric relationships to find the angle of projection and analyze vertical motion to determine the vertical component of initial velocity. There are attempts to apply kinematic equations, with some questioning the correctness of their approach and the use of average versus initial velocities.

Discussion Status

The discussion is ongoing, with participants providing guidance on the use of kinematic equations and clarifying concepts related to average speed and time calculations. There is an exploration of different methods to find time and initial velocity, with no explicit consensus reached yet.

Contextual Notes

Participants are navigating the complexities of projectile motion, with some expressing uncertainty about the application of formulas and the distinction between average and initial velocities. The discussion reflects a learning process with varying levels of understanding among participants.

  • #31
one revolution = 2*pi radians

31.5 / 2*pi = just over 5 revolutions :)

but i had to find 2*pi first then use that answer to divided into 31.5 rads.. otherwise the answer will be completely different for some reason.

As for average angular speed:

20 / 2 = 10 rpm?
 
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  • #32
Milkster18 said:
one revolution = 2*pi radians

31.5 / 2*pi = just over 5 revolutions :)
Good.

but i had to find 2*pi first then use that answer to divided into 31.5 rads.. otherwise the answer will be completely different for some reason.
Not sure what you mean.

As for average angular speed:

20 / 2 = 10 rpm?
No. It goes from 20 rpm to 40 rpm, so what would the average be? (It can't be 10 rpm!)
 
  • #33
Ah

W1 + W2 / 2

20 + 40 / 2 = 30 rpm

So now i have average how does this make things easier?

Im from the UK by the way so i think some units / symbols are different to US if your from there.

Thanks for the help again. :)
 
  • #34
Milkster18 said:
Ah

W1 + W2 / 2

20 + 40 / 2 = 30 rpm
Good.

So now i have average how does this make things easier?
Use the same formula as before: Distance = ave speed X time
Here "distance" is replaced by angle/revolutions.

Hint: How many minutes is 10 seconds?
 

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