Conservation of energy and centripital force

AI Thread Summary
The discussion focuses on calculating the force exerted by a mass sliding within a hoop at a specific angle. The mass is 0.5 kg, and when at the top of the hoop, it has a speed of 5.65 m/s. The user applies conservation of energy to find the speed at an angle of 27 degrees, resulting in 5.88 m/s. They calculate the centripetal force to be 23.07 N but encounter confusion regarding the free body diagram and the relationship between centripetal force, normal force, and gravitational force. Clarifications are sought on the correct approach to resolving forces at the given angle.
Megz27
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The Question is:

A mass M of 5.00×10-1 kg slides inside a hoop of radius R=1.50 m with negligible friction. When M is at the top, it has a speed of 5.65 m/s. Calculate size of the force with which the M pushes on the hoop when M is at an angle of 27.0 degrees.

My workings thus far:

1st i know i have to use the radius and theta to get the distance of the mass below the hoop
then i have to use the speed at the top and the conservation of mechanical energy to get the speed of the mass at theta
then i make a fbd and get the normal force

so
using trig
1.5 cos 27= x
x= 1.3365m (distance under center of hoop)
distance from bottem then equals 0.1635 m as the hoop is 1.5 m in radius

so using conservation of energy i get
total energy top= total energy bottem
potentical energy top + kE top = pot Energy bottem + Ke bottem
mgh + 1/2 mv^2 = mgh+1/2mv^2 (all masses cancel out
(9.81)(3) +1/2(5.65)^2 = (9.81)(0.1635) + 1/2 v^2
solve for v = 5.88223 m/s

so the speed at theata is 5.88223 m/s, then using centripical force =mv^2/r we can get 23.067 N for the force.

Then we draw a free body diagram and we get that Fc=Fn (what were looking for)+ Fg
This is were i get stuck..
Help from here??
 
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Welcome to PF!

Megz27 said:
… when M is at an angle of 27.0 degrees

Then we draw a free body diagram and we get that Fc=Fn (what were looking for)+ Fg …

Hi Megz27! Welcome to PF! :smile:

i] 27.0 degrees from what? :confused:

ii] Fc = Fn + Fg is not correct.
 
27 degress from the bottem of the circle..

how would you approach the FC is that is not correct?
 
Megz27 said:
then i make a fbd and get the normal force

What does your fbd look like?

In which direction are you taking components?

What equation does it give you? :smile:
 
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