# Questions tagged [forces]

This tag is for the classical concept of forces, i.e. the quantities causing an acceleration of a body. It expands to the strong/electroweak force only insofar as they act comparable to ‘classical’ forces. Use the [particle-physics] tag for decay channels due to forces and [newtonian-mechanics] or one of the other subtopics of [classical-mechanics] for the dynamics of classical systems.

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### Newtons Third law - does it apply regardless of size difference between interacting bodies?

This is a theoretical question. Assume I have a $1000 \;\text{kg}$ box and just 1 molecule (say Oxygen) in a 100-meter-tall hollow vertical cylinder. The cylinder walls are much wider than the box ...
5answers
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### Example on impulse

A rubber ball of mass $50g$ falls from a height of $1m$ and rebounds to a height of $0.5m$. Find the impulse and the average force between the ball and the ground if the time for which they are in ...
2answers
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### Tension force and Newton's third law

When a horse pulls a cart, suppose connected by a string, it produces a tension $T$ in the string. The cart in turn pulls the horse by an equal force $T$ in the opposite direction. If this T>f, the ...
2answers
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### Help me in understanding use of vector in this problem

In the question here, velocity of block A is $5 \;\text{m/s}$. To find the velocity $v$ of block B, why do we use $v \cos 53° = 5$ instead of $5 \cos 53° = v$. Isn't the $5 \;\text{m/s}$ velocity ...
1answer
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### How can the $x$-components of the frictional force and the normal force be the same for a static block on an incline? [closed]

I recently was assigned this problem as part of my homework: "A block sits on a plane that is inclined at an angle $\theta$. Assume that the friction force is large enough to keep the block at ...
3answers
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1answer
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### Why do ants feel more difficult to climb when height increases? [closed]

I have noticed that whenever an ant (carrying something) climbs a vertical wall, it easily climbs the lower part of the wall but as the height increases, the ant finds it difficult to climb and at ...
1answer
42 views

### The behaviour of acceleration of a ball in motion

I have a few doubts on how the acceleration of a ball works when we throw it up in the air, In my mind, I could imagine it in some different "real world" cases, So I am listing them all down,...
4answers
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### Law of conservation of momentum and force

It is said that internal forces do not change the state of rest to motion only external forces can change it. But in case of a gun, a gun applies force internally to the bullet inside it and the ...
0answers
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### Absorption chillers: can they achieve temperatures below zero Celsius?

If I understand correctly (history shows I probably don't), then the only reason why the absorption chiller evaporators are restricted (I hope that's the right word) to extract just enough heat so the ...
3answers
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### Why is the normal force and the tension force greater than the weight in these examples? [closed]

A pendulum is suspended form the roof of an accelerating train. If it stays in equilibrium with respect to the train then an observer at rest will find the bob accelerating with the train. He will ...
1answer
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### The projection of the Newton law for a ball moving in an italic direction

if I want to push the bowling ball in a direction which is not parallel to the lane, then I need to make a Projection on the axes (the x axis is parallel with the width of the lane and the y axis is ...