Recent content by Steve4Physics

Hi @sol_2001. For simplicity just consider cooling by convection. Suppose the air temperature is 25##^\circ## and your skin’s surface temperature is 30##^\circ##C. You will be cooled by natural convection. But it may not be enough for you. Heat transfer by convection depends (amongst other...

Hi @neilparker62, Here are a few additional comments - just in case the presentation will be given again. ______________ Some references to ‘distance’ should be to “displacement”. Similarly for ‘speed’ and ‘velocity’.The distinctions are important. E.g. in the slide “The Symmetric Equations”...

No need to apologise! I’m not familiar with. Surface Engineering so can't help much. I'll add a few questions/ comments and then hopefully leave it to someone who knows what they're talking about. It might help if you said what text book you are using and/or where the question comes from...

Hi @LUFER. Your post is difficult (for me at least) to follow. Here are some comments... In the original question the phrase, "a power of 5 x 10⁻⁵ W/µm²" is wrong. The quantity 5 x 10⁻⁵ W/µm² is an intensity, not a power. The wording refers to "a surface" and to "the particle". This is...

How do you tell the difference between a physicist and a trade-union leader?

Yes, Thanks. I see my mistake in Post #6. I overlooked the (obvious!) fact that the pulley itself has a vertical acceleration of ##A_y##. I don't think your explanation is too hand-wavy! m’s vertical acceleration is the vector sum of: - the vertical acceleration of the pulley (A_y) and -...

In addition to what @TSny has suggested, you could try this... Let ##A_x## and ##A_y## be the horizontal and vertical components of M’s acceleration. (##\frac {A_y}{A_x} = \tan \alpha##). Let ##a_x## and ##a_y## be the horizontal and vertical components of m’s acceleration. ##A_x =a_x ##...

Aagh. Misread the question. Post struck-through.

Of course, relativistic effects need to be accounted.... Edit - please ignore. misread question.

In the connected situation (S1 and S2 joined) condition 1 applies: Torque (S1) = Torque(S2) = 0 If any object - even if it is part of a larger object - has zero angular acceleration (##\alpha##), e.g. if the object is stationary, then the net torque (##\tau##) on the object MUST be zero...

You are comparing two different systems – not two versions of the same system. So your comparison isn’t valid. I'll try to explain why. In the initial system, you have two motors ##M_1## (trying to make rod rotate clockwise (CW)) and ##M_2## (trying to make rod rotate anticlockwise (ACW)). The...

Here in the UK, building insurance often excludes cover for damage caused by infinite forces. For this reason, all our builders and carpenters now receive mandatory physics training in order to reduce the risk of incorrectly positioned PUSH (and PULL) signs.:smile:

A couple of thoughts... No. If a ’subsystem’ had non-zero torque, then it would have some angular acceleration. @anuttarasammyak, you don’t have to worry about infinite forces here! Consider a simple case: a horizontal bar of negligible weight, supported at one end by a hinge and carrying a...

To add to what’s already been said, you are correct but it doesn't matter. If you calculate ##F_y## you will get a negative value. You will then know the actual direction is opposite to the initial ‘guess’. This approach is valuable in complicated systems, where it may not be easy to find all...

It might help to remember that there are two types of equilibrium – translational and rotational. In this question, in the horizontal direction, translational equilibrium requires that ##D \sin(55^\circ) = F##. Part of D’s ‘physical affect’ is to contribute to translational equilibrium. Now...