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Some general questions

Why do gases float? They have mass so surely they have weight and fall due to gravity?

If the sun were to just disappear how long would it take for Earth to go off at a tangent? Would it be instantaneous or would it take like 8 minutes (same as light)?

Why are planets and stars spherical?

Does gravitational field strength get weaker as you travel further away from Earth? How far do you have to be to have no gravitational effects?

What determines gravitational field strength? Would a more massive planet have greater g?

If I punch someone what determines how much it hurts? Is it the force of the hit, the kinetic energy, its momentum or its power?

Does gravity do work?

If you have displacement you can use calculus to differentiate with respect to time in order to find velocity, right? Can this only be done when you have an algebraic expression for displacement in terms of time? Does this have any application in real life where you can't really have an expression for displacement?

If something is constantly changing velocity how is it possible to find the velocity at say exactly 10 seconds? v = s/t so surely you need it to be traveling some and taking some time so you'd really be taking velocity between say 9.9 seconds and 10.1 seconds wouldn't you?

Reply 1

teachercol

The upthrust due to the weight of the air displaced is greater than their weight

Yes - gravity 'travels' at the speed oflight

Gravitational forces minimise the potential energy as they condensed (but rotation flattens them slightly)

forces are prop to 1/r^2. They extend to infinity (and beyond)

g depends on the mass and the size of the planet ( = G M / R^2)

Dunno

Can do - if something is falling,; not if not moving eg an object on a table

Integration can be done numerically as well as algebraically. - in fact it usually is in real world situations.

Ask Zeno.