Stars other than our sun normally appear featureless when viewed through telescopes. Yet astronomers can readily use the light from these stars to determine that they are rotating and even measure the speed of their surface. How do you think they can do this?
I used the "Inside a solid sphere of constant density the gravitational force varies linearly with distance from the center, becoming zero at the center of mass."
from the reference to make my previous suggestion and yes I did get intimidated when I scrolled down from there. Can someone...
Yea that does help...thanks...but what about question c? Was I right about that? When an object falls some of the PE gets translated into KE which slows the object down right?
What happens to the "lost" energy in these situations?
(a) A box sliding across the floor stops due to friction. How did friction take away that KE and what happened to that energy?
(b) A car stops when you apply the brakes. What happened to its kinetic energy?
(c) air resistance uses up...
A 1 Kg object is dropped from rest from a helicopter at an altitude
of 2000 meters. What is the velocity of the object just before it lands upon a thick bed of pillows? The top of the pillow stack is at zero altitude. If the restoring force
constant (spring constant) of the stack of pillows is...
You dig a hole half way to the center of the earth. You lower an object to the bottom
of the hole. By what fraction has the force of the Earth’s gravity on the object been reduced
relative to that at the surface? Assume that the earth is a sphere and has uniform density
.5*density *(0)2 + 0 + 10atm(convert) = constant
(.5)(density)(vf)2 + density(g)(y height) + 2atm
Would I set these equal and solve for vf??
What about the height of the lake and the height of the pipe?? Do those add more pressure??
An object is accidentally dropped into a water pipe. Pressure applied to pipe is 10 atm. The depth of lake is 10m. What will be speed of object when it exits the pipe and first enters the lake? Assume that the object is carried along with the surrounding water and does not affect flow of...
I know tau = r x F
would you plug 1N for F? and 1 m(radius of sphere) for r?
tau = 1N x 1m = 1 N m
I = (2/5)(100kg)(1m)^2 = 40 kg m
so
angular acceleration = tau/I = (1/40) rad/s^2
is this right?
How would u use coeff of friction?
Initial angular velocity = 100 rev/s
Final angular velocity = 0
I don't know how to get the angular acc.
Would you use the torque formula?
tau = Iα ?
I don't know what tau would be
How does it show that neither are conserved? Is it because the result is not the same at the top of the swing and the bottom of the swing in both cases?
Wouldn't angular momentum be conserved since the Sun doesn't apply any torque to the planet?
dL/dt = tau = r cross F
r is vector from sun to planet
F is directed from planet to sun
so cross product would be 0
resulting in constant angular motion
A pendulum swings through a maximum arc of one degree in 1 sec. Later, the pendulum is made to swing through a max of 2 degrees. What is the time required for the 2 degree arc?
T = 2pi(L/g)^(1/2)
Is the time the same since the swing depends on only the length and gravity due to acceleration?
x is the cross product in this case.
Is r cross product 0 = 0?
Sorry I kind of forgot cross product ...so I'm not sure
rockfreak, sorry maybe I shouldve restated it in the actual post but the topic title is "pendulum swing conserves what?"
So we usually talk about Kelvin at around 273K and above which prevents using 0K. Isn't the Kelvin scale directly related to pressure since 0K = 0Pressure? but at zero pressure the celsius scale has a negative value.