Projectile Motion (Initial Velocity)

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SUMMARY

This discussion focuses on calculating the initial velocity of a projectile, specifically a ball kicked from point A to clear a wall at point B. The problem involves determining the initial vertical velocity (Uy) using kinematic equations, specifically Vy² = Uy² - 2g(Sy), where g is the acceleration due to gravity (9.81 m/s²) and Sy is the vertical displacement (4 m). The final calculated initial velocity is 23.9 m/s, derived from the horizontal (Ux) and vertical components (Uy) using the Pythagorean theorem.

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  • #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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