kastamonu

I found N1 as 16. I couldn't find N2. How will I find it?

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studiot

Is box k in equilibrium?

Can you draw a free body diagram for it?

(Do you know what a free body diagram is? If not say so , it is something you need to know)

kastamonu

Many Thanks.I found the answer. What is a free body diagram?

benit13

Your little diagram is like a free-body diagram (just an incomplete one). A free-body diagram is a schematic diagram with all of the objects in your system which are subject to or exerting forces with arrows indicating where the forces are applied and with what magnitude.

You need to add to your diagram the weights of the boxes. They should be drawn as arrows coming from the centre of mass (usually just a middle point) of those objects and facing in the correct direction (in this, it will be down towards the ground). Then you can start considering each object and work out what the contact forces should be to preserve equilibrium.

So... consider box L. There are three forces involving L:

1. The weight of the box (8 N downwards)
2. The pushing force on the top of the box (4 N downwards)
3. The contact force of K (? N upwards)

So... if the box is stationary, we know that, because of Newton's first law, the net force must be zero. In other words, the upwards forces must balance the downwards forces.

Can you now calculate the contact force?

After you've calculated that, you can then do the same for box K. Remember that the weight of box L is applied to it and the floor is pushing up on the box as well as the box having its own weight.

To double check your answers, you can do another calculation considering both boxes as a combined system (like one big box with a weight of 12 N) and the forces should still balance.

HallsofIvy

Since Kastomuno says he has solved this problem and probably won't be back here, here is how I would solve this: There is an object with weight 8 N sitting on the ground with an object with weight 4 N on top of it and then there is a force of 4 N pushing down on that. So there is a total of 16 N pressing on the ground and the ground will press back upward with 16 N. That is "N1". The total force on the 8 N object is 8 N, the weight of the top object plus the additional force. The 8 N object presses back up on the top object with force 8 N. That is "N2". The ratio is 16 N/8 N= 2.

kastamonu

I solved the problem. Many Thanks.

HallsofIvy

Hey, you're back! Thanks!

Pmb

Why does the subject line say Newton's rules? There's no such thing. You must mean Newton's laws. Careful here. Thete is quite a difference between a law and a rule.

HallsofIvy

How about "Newton's suggestions"?

Pmb

There is something callef "Newton's rule" but that's a math thing, not physics. If you search newton's ruels with google it will nring up pages about newtons law. Laws are quite different than rules.