Conservation of energy and centripital force

In summary, the question is asking how to calculate the force with which a mass (5.00×10-1 kg) slides inside a hoop (radius 1.50 m) with negligible friction. The answer is that the force is 23.067 N.
  • #1
Megz27
5
0
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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  • #2
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.
 
  • #3
27 degress from the bottem of the circle..

how would you approach the FC is that is not correct?
 
  • #4
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:
 

1. What is the law of conservation of energy?

The law of conservation of energy states that energy cannot be created or destroyed, but it can be transformed from one form to another. This means that the total energy of a closed system will remain constant over time.

2. How does conservation of energy relate to centripetal force?

Centripetal force is the force that keeps an object moving in a circular path. According to the law of conservation of energy, the total energy of the object must remain constant. This means that as the object moves in a circular path, its kinetic energy may decrease, but its potential energy will increase to compensate. This ensures that the total energy of the object remains constant.

3. Can centripetal force be greater than the force of gravity?

Yes, it is possible for the centripetal force to be greater than the force of gravity. This typically occurs when an object is moving in a circular path at high speeds. In this scenario, the centripetal force must be strong enough to counteract the force of gravity and keep the object in its circular path.

4. How is conservation of energy and centripetal force used in real life?

Conservation of energy and centripetal force are used in a variety of real-life applications. For example, roller coasters use centripetal force to keep passengers safely in their seats as they move through loops and turns. In space, conservation of energy is essential for maintaining the orbit of a satellite around a planet.

5. Are there any exceptions to the law of conservation of energy?

There are a few exceptions to the law of conservation of energy, such as in nuclear reactions or when dealing with subatomic particles. In these cases, energy may be created or destroyed, but this is due to the conversion of matter into energy, as described by Einstein's famous equation, E=mc².

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