Recent content by garylau

using the centre of mass frame we can let the total final KE =0 because both object moves with the centre of mass and just find the initial KE ?

If i use the centre of mass frame to do this question Will i got it easily?

thank but this way looks to complicated Do you have other method to do this question thank for example: do it in the centre of mass frame or using the conservation of energy??

https://www.algebra.com/algebra/homework/word/travel/Travel_Word_Problems.faq.question.1040713.html It starts at zero and accelerates to 45 m/sec --> avg speed = 22.5 m/sec ----- t = d/r = 1.5/22.5 = 1/15 second ======== Acceleration = 45 m/sec/(1/15 sec) = 675 m/sec/sec

https://www.google.com.au/search?q=%22The+fastest+measured+pitched+baseball+left+the+pitcher%27s+hand+at+the+speed+of+45%22&oq=%22The+fastest+measured+pitched+baseball+left+the+pitcher%27s+hand+at+the+speed+of+45%22&aqs=chrome..69i57.1143j0j7&sourceid=chrome&ie=UTF-8#q=%22The+fastest+measured+pit...

1. Homework Statement A small mass m slides without friction on a surface making a quarter-‐circle with radius R, as shown. Then it lands on the top surface of a cart, mass M, that slides without friction on a horizontal surface. (In practice, this cart could be a slider on an air-‐track.)...

i have found one article state something like this:"""Any real evolution (macroevolution) requires an expansion of the gene pool, the addition of new genes (genons) with new information for new traits as life is supposed to move from simple beginnings to ever more varied and complex forms...

for these cases, you could define x as the displacement from the force to the axis, up being positive. how about the vector x pointing in random direction?

So in my original problem the sign of R/r should be negative so that i can get the correct answer?

then horizontal force F to the right should be negative?? it seems it is contradicted with the "other sign of convention"(which usually we take right side to be positive and left side to be negative)

but in convention the anti-clockwise direction is the positive direction of the torque,right?

oh i see thank But how to make the sign of the torque and the sign of the net force consistent in general?

Homework Statement The sketch shows, from two views, a simple pulley system for raising large masses. A light, inextensible cord attached to a mass m is wound, without slipping, on a cylinder of radius r. Rigidly joined to this cylinder and mounted on the same central shaft is a cylinder of...

Sorry there are two different solutions in one question ! which one is correct?? the first one is written by griffiths the second one is written by a lecturer. they are not consistent in the same question So which one is correct? thank you

yes i should remove in the integral but i always forget thank you