Newton's Laws of Motions........?

Question

1. How can I relate any of the three Newton's law to pressure, friction, fluid, air resistance or the freely falling object. (Give me an example of any of them)

2. What is the formula for each law? (I heard something like a=F/M)

PLEASE HELP !!! I REALLY NEED TO KnOW THIS !!!!

Thanks !!!

Answer 1

Answer 2 first because it serves as the basis for 1.

2. Law 1...inertia; measured by momentum p = mv; where m is mass and v is velocity.

Law 2...force: F = dp/dt = m dv/dt = ma; where dv/dt = a = acceleration. Thus, force is just a change in momentum (Law 1) over time.

Law 3...for every action there is an equal but opposite reaction. f = sum(all forces) = 0 if and only if the mass is not accelerating; so that f = ma = 0. [See free falling body next.]

1. Pressure P = F/A = mg/A; where A is area the force F is acting on. g = acceleration due to gravity (9.81 m/sec^2) When F = mg, we call that force weight F = W = mg.

f = PA - F = PA - kmg cos(theta) = 0; where friction force = F = kmg cos(theta) and k = coefficient of friction, g = 9.81 m/sec^2, and theta is the incline angle of whatever platform the object with friction is on. The net force f on an object is the push (PA) minus the force of friction (F) acting in the opposite direction.

Air and fluid resistance (called drag) have similar equations D = 1/2 rho g Cd A v^2; where rho is air mass density, Cd is a coefficient of drag, A is cross sectional area of the object, and v is relative velocity wrt air. Fluid has a similar equation.

f = W - D = mg - 1/2 rho Cd A v^2 = ma; which is the net force acting on a freely falling body of weight W = mg. When W = mg = 1/2 rho g Cd A v^2 = D, the freely falling body is no longer accelerating downward because we have f = W - D = 0 = ma such that a = 0. The falling object has reached terminal velocity which remains constant until impact.

Answer 2

a'ight,
part 2
newton's 1st law is concerning INERTIA(every obj in the univ.
continues to stay at rest or maintain a steady motion, until & unless an external unbalanced force is applied.)
2nd law- the law of momentum i.e F=m x a (force=mass * accelaration)
3rd-every action has an equal & opp. reaction.