Recent content by walter1998

Can you demonstrate it in a diagram?or give a link of it?

OK then, whatever it is just explain it!

http://www.physics.ucla.edu/demoweb/demomanual/mechanics/momentum_and_collisions/weight_of_an_hour_glass.html

W=mg that is what weight is. I think that when the sands are falling it is a kind of free fall; so some of the hourglasses's weight should diminish.

How does an hourglass's weight change while sand is dripping in it? (better be in a diagram)

This question is asked in a famous competition in my country: "Approximately calculate the diameter of the lens which this picture is taken with.(for measurements consider lens as a flat object) "

I think it is possible but i cannot prove it; I'd be glad if you could guide me or more glad if you solve it.

longer means the longest arc available. and the star is not important, just the declination is the thing.

People in the past thought that a city which the length of the visible arc of a star's path in that city is longer, that city is the luck city; Now, for a city with a latitude of 35° how much should be the star's declination to be the luck city?

Consider a pendulum in it's balance point hanging from ceiling. It can swing in all the directions in the space. The pendulum can only swing in a sphere(the string can't bend). Now, is it possible to release the pendulum in a particular height and with a initial condition that in the first...

Hello guys, I was wondering if you could guess or even calculate the diameter of a camera lens with a picture of a ruler.