What are the Maximum Speeds of a Pendulum with Attached Mass?

In summary, the conversation discusses the calculation of the maximum speed in the x and y directions for a pendulum with given values of mass, height, and length. The conservation of energy and vector components are used to derive expressions for the velocities. The need for the initial value of theta is discussed, with the conclusion that it is not necessary for the calculations.
  • #1
SherlockOhms
310
0

Homework Statement


A pendulum of mass "m" reaches a height "h" , while the length of the pendulum is R. If the R = 262 cm and h = 136 cm: (a) calculate the max speed in the x-direction.
(b) calculate the max speed in the y direction.


Homework Equations


K = 1/2(m)(v)^2.
U = mgh.
Vector components.

The Attempt at a Solution


Calculating the max speed in the x direction is grand, it obtains a maximum value at the bottom of the arc so using conservation of energy you can calculate it to be v = sqrt(2gh). This is due to the vector components of the pendulum's velocity being v = vcos(θ)x + vsin(θ)y. The x-component obtains a max value when cos(θ) = 1 which occurs at θ = 0 (i.e. the bottom of the arc). Wouldn't the y-component then obtain a max value when θ = pi/2? This angle is never actually reached due to the bob only being raised through a height "h".
So calculating the max velocity in the y is a little trickier. Could somebody give me some advice on what to do next? I'll attach a picture of the diagram.
 
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  • #2
ImageUploadedByPhysics Forums1366399180.541798.jpg
 
  • #3
You should be able to write down an expression for the potential energy of the mass as a function of ##\theta##. Using it, you can derive an expression for v as a function of ##\theta##.
 
  • #4
vela said:
You should be able to write down an expression for the potential energy of the mass as a function of ##\theta##. Using it, you can derive an expression for v as a function of ##\theta##.

I'm not given θ though. Is there enough information given to find it?
 
  • #5
##\theta## is a variable that tells you where the pendulum is. It changes with time. Did you mean ##\theta_0##, the initial value of ##\theta##? You are, in fact, given enough information to find it, but I'm not sure why you'd need it.
 
  • #6
Ok, ok. I see what you're saying now. Misunderstood your first reply. Thanks!
 

1. What is a pendulum with mass attached?

A pendulum with mass attached is a physical system that consists of a mass attached to a pivot point by a string or rod. The mass is allowed to swing back and forth under the influence of gravity, creating a regular and predictable motion.

2. What factors affect the motion of a pendulum with mass attached?

The motion of a pendulum with mass attached is affected by several factors including the length of the string or rod, the mass of the object, and the angle at which it is released. Other factors such as air resistance and friction can also have an impact on the motion.

3. What is the equation for the period of a pendulum with mass attached?

The equation for the period of a pendulum with mass attached is T = 2π√(l/g), where T is the period (time for one complete swing), l is the length of the string or rod, and g is the acceleration due to gravity.

4. How does the mass of the object affect the period of a pendulum with mass attached?

The mass of the object has no effect on the period of a pendulum with mass attached. This is because the mass cancels out in the equation for the period, meaning that a pendulum with a heavier or lighter object will have the same period as long as the other variables (length and angle) remain constant.

5. What is the use of a pendulum with mass attached in science?

Pendulums with mass attached are used in science for various purposes, including measuring time (such as in grandfather clocks), demonstrating principles of harmonic motion, and as a tool for investigating the effects of gravity and other forces on a system. They are also used in seismometers to detect and measure earthquakes.

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