Vishesh N.

The angle is 45 degrees

Watch this video made by me to understand the concept better

https://www.youtube.com/watch?v=N4l0hJ9x4Tg&list=PLQgL7RKnNg_yrgYAhTNAEoshDNDHDBAWr&index=4&t=7s

Equate F (net) = ma

Then    T - mg = ma   (assume all vectors in + Y direction as positive)

           33000 - 3000 X 9.8 = 3000 a

           a = 1.2 m/s²

This essentially means that the net force on the elevator is making it move up with an acceleration of 1.2 m/s²

See my lecture notes for a better understanding

Let's say you push the wooden block, it is true the the block pushes you back with the same force. However, this does not mean that the force that you are exerting on the block has got cancelled. The wooden block will continue to to experience the push and so would you from the block being pushed. In a way they are 2 separate forces, each acting on separate object.

To understand the concept better imagine yourself pushing your friend and your friend pushing you back with the same force. Just because the forces are equal and opposite in magnitude, does not mean that you feel at ease. You feel the pain in your muscles because there is a force acting on your arms that stresses your muscles.

Scientifically put, you need to see the body being pushed in isolation. The force you are putting on the body is “tangible” and makes it move once the force of friction has been overcome.

This is the reason problems around Newton’s laws of motion are solved by using “free body diagrams”. This essentially requires you to label all forces that act on a body and then find the “Net force”, using vector algebra. This net force is then equated with the product of mass and the acceleration this net force is creating, to find the unknown in the equation. 

Put yourself on a weighing scales inside a stationery elevator. So your velocity here is zero meters per second. Let us examine what are the forces acting on your body. We know one of the force is “mg” which acts in the downward direction.The weighing scale will push you up with a certain force which is nothing but the Normal reaction and shows up as weight “W” on the weighing scale (We will take any vector pointing in the upward direction as positive and any vector acting in the downward direction as negative).

We write the forces acting on your body in accordance with Newton's second law of motion which says that the net force acting on you or on a body is equal to its mass into the acceleration induced or

F net = m X a

There are 2 forces acting on the body  (1) mg acting in downward direction and we take it as a negative vector and (2) The normal reaction from the floor lift that is the weight or W (we take it as a positive vector since it points upwards)

So the net force is = W – mg and this should equal the product of resultant acceleration with mass. So the equation that will form is

          F net = W - mg = ma

Or                  W = mg + ma

So if the lift is stationery, a = 0 and W = mg the way it should be. You simply see your weight in the scale

But if the lift starts accelerating up so that velocity increases resulting in positive acceleration “a”. We see that the entity “ma” in above equation adds to mg and therefore the weight W increase.

But if the lift is moving up with a uniform velocity, acceleration “a” will become zero (since acceleration happens only when velocity changes). In such a case again, W = mg or no change

Now imagine that you are reaching the top floor. The lift will start slowing down and this can happen only if a force acts on the lift in the opposite direction. Hence the acceleration “a” now is in downward direction hence negative. So the above equation will now become

W = mg + m X (-a) or

W = mg – ma

So you see when the lift is slowing down at the top, your weight will now reduce by “ma”.