Mechanics Problem using Polar Coordinates

In summary, the first part is really long and I don't understand it, and the second part is very difficult for me. I don't know what to do. Please help me.
  • #1
MathDestructor
15
0
Homework Statement
I don't know how to take polar derivatives.
Relevant Equations
r = Rcos(theta) + Rsin(theta)
1580492747754.png


1580493310652.png

This is what I have so far, please need urgent help. I don't understand and know what to do.

For the first part, I got a really long answer, for the second part I am trying in terms of mv^2/r = mg, or mg = m*(answer to first), but I am getting nowhere. PLease help
 
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  • #2
Please show your work. We don't give answers away but point out mistakes.
 
  • #3
1580493253059.png
This is all I have, I don't know what to do after, I've been stuck for 2 days, and its due in half an hour.
 
  • #4
MathDestructor said:
This is all I have, I don't know what to do after, I've been stuck for 2 days, and its due in half an hour.
As long as the bead stays on the surface ##\dot R## = 0. That should simplify things for you.
 
  • #5
Is my second derivative right?
 
  • #6
What forces should I use to try and solve the second part.
 
  • #7
MathDestructor said:
What forces should I use to try and solve the second part.
Please show the revised velocity and acceleration in view of my comments in post #4. You cannot proceed to the second part unless you get the first part right. If you have to post pictures (a practice we discourage) at least make sure they are right side up.
 
  • #8
1580493893133.png
 
  • #9
I tried mv^2/r = mg and mr''= mg. None of them are working
 
  • #10
MathDestructor said:
I tried mv^2/r = mg and mr''= mg. None of them are working
You need to write a vector equation. How many different forces act on the bead when it is on the surface at angle φ? Write their vector sum in unit vector notation and set it equal to ##m\vec a## in unit vector notation. Your expressions for the velocity and acceleration are correct.
 
  • #11
kuruman said:
You need to write a vector equation. How many different forces act on the bead when it is on the surface at angle φ? Write their vector sum in unit vector notation and set it equal to ##m\vec a## in unit vector notation. Your expressions for the velocity and acceleration are correct.
I don't know what that means, or how to do that.
 
  • #12
I have 10 mins left, I would really appreciate it if you would help me in a hurry just this once. Please.
 
  • #13
MathDestructor said:
I have 10 mins left, I would really appreciate it if you would help me in a hurry just this once. Please.
Sorry, it is against forum rules. Do your best. Identify the forces that act on the bead, draw a free body diagram and use it to write each force in unit vector notation.
 
  • #14
I know this doesn't give you an answer, but, you can just google for Polar Coordinate Vector System Derivation.
I did that and it all finally made sense.
Some YouTube videos also helped.
It wasn't a part of my curriculum so far, but, learning it helped me understand so many things that, as a result, I have become near-invicible when it comes to inclined plane problems.
 

Related to Mechanics Problem using Polar Coordinates

1. What are polar coordinates and how are they used in mechanics problems?

Polar coordinates are a type of coordinate system that is used to describe the position of a point in a plane. They consist of a distance from the origin (known as the radius) and an angle from a reference direction (usually the positive x-axis). In mechanics problems, polar coordinates are used to describe the motion of objects in a circular or curved path.

2. How do you convert between polar and Cartesian coordinates?

To convert from polar to Cartesian coordinates, you can use the following equations: x = r * cos(θ) and y = r * sin(θ), where r is the radius and θ is the angle. To convert from Cartesian to polar coordinates, you can use the equations: r = √(x^2 + y^2) and θ = tan^-1(y/x).

3. What are some common applications of polar coordinates in mechanics?

Polar coordinates are commonly used in mechanics to describe the motion of objects in circular or rotational motion, such as the swinging of a pendulum, the rotation of a wheel, or the orbit of a planet around a sun. They are also used in problems involving forces acting at an angle, such as in projectile motion.

4. How do you solve mechanics problems using polar coordinates?

To solve mechanics problems using polar coordinates, you first need to identify the variables involved, such as the radius, angle, and velocity. Then, you can use equations such as Newton's second law or conservation of energy to analyze the motion of the object. It is important to keep track of the direction of the forces and velocities, as they are represented by angles in polar coordinates.

5. What are some advantages of using polar coordinates in mechanics?

One advantage of using polar coordinates in mechanics is that they are well-suited for describing circular or rotational motion. They also make it easier to analyze forces and velocities that are acting at an angle. Additionally, polar coordinates can simplify equations and calculations in certain mechanics problems, making them more efficient to solve.

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