Clueless in physics please help?

Question

I've missed the last 2 lectures for my physics course all I have is a printout of the problem w/o a book to read over. Can someone please answer these questions and provide some feedback as to what/why. Thanks:)

(a) An elevator of mass m moving upward has two forces
acting on it: the upward force of tension, cable and the downward of gravity. When the elevator is accelerating upward, which is greater, T or w?
(b) When the elevator is moving at a constant velocity upward, which is greater, T or w?
(c) When the elevator is moving upward, but the acceleration downward, greater? T or w?
(d) Let the elevator have a mass of 1500 kg and an upward acceleration of 2.5 m/s2. Find T. Is answer consistent with answer to part (a)?
(e) The elevator of part (d) now moves with a constant upward velocity of 10 m/s. Find T. Is your answer consistent with your answer to part (b)?
(f) Having initially moved upward w/a constant velocity, the elevator begins to accelerate downward at 1.5m/s2. Find T

Answer 1

First, an object in motion tends to stay in motion unless an outside force acts on it. This is one of Newton's laws.

Second, F=ma, Force = mass x acceleration.

Third under all circumstances, weight= m*g therefore,
T= m*g +/- m*a

Ok, let's start:

a. The elevator is accerating upwards. Using F=ma, we know that the NET force is upwards (otherwise it would not accelerate upwards). Therefore T is greater.

b. Constant velocity. No net force per Sir Isaac Newton. Also, no acceleration per F=ma. Therefore no net force. Therefore T= w.

c. Elevator up but slowing. Acceration is downward (even though the elevator is still going up), therefore net force is down and w is greater.

d. F=ma. T=m*g+m*a
= 1500kg *9.8 m/sec^2 + 1500kg *2.5 m/s^2
=18,450 N
Yes. Weight is simply 14,700 N

e. F= ma
T=mg
= 14700 N
Yes

f. T= mg - ma
= 1500* 9.8 - 1500* (-1.5)
= 12,450 N

I hope I have been clear. Good luck