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 [tag:particle-physics] for decay channels due to forces and [tag:newtonian-mechanics] or ...

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Given a potential energy function, find expression of the force of a particle?

This comes from an AP review packet. I'm given a potential energy functon, $$U(r)=br^{-3/2} + c,$$ where $b$ and $c$ are constants, and need to find the expression for the force on the particle. ...
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408 views

effect of vertical collision on kinetic friction and subsequent change in horizontal velocity

Suppose somehow a block of mass $m$ is moving on ground, and the coefficient of kinetic friction between the block and the block is $\mu_k$. If I drop a tennis ball(of same mass) on it from a ...
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1answer
115 views

Static Friction work and Energy [closed]

I have this problem: A 4.0 kg block is given an initial speed of 8.0 m/s at the bottom of a 20° incline. The frictional force that retards its motion is 15.0 N. (a) If the block is ...
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200 views

Additional mass of block on inclined plane

I would like some help in solving this problem. Height is 15 cm , base is 88 cm My attempt: $$(119.3 + m)(\sin(\theta)) = (88*9.8)$$ $$ 15^2 + 88^2 = 89.269^2 $$ $$ \sin^{-1} = 15/89.269 $$ $$ ...
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1answer
918 views

Gravity force strength in 1D, 2D, 3D and higher spatial dimensions

Let's say that we want to measure the gravity force in 1D, 2D, 3D and higher spatial dimensions. Will we get the same force strength in the first 3 dimensions and then it will go up? How about if ...
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383 views

Opposing forces on an air cylinder — half force each or full force each?

If an air cylinder is pushing two platens apart with a force of $100\: \mathrm{lbs}$, do the platens need to push back at $100\: \mathrm{lbs}$ or $50\: \mathrm{lbs}$ each to keep the cylinder from ...
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287 views
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284 views

Is it easier to move or rotate an object? [closed]

This is a problem I'm facing on designing a moving bookcase for my home, I just don't have enough physics background to tackle the problem. Which of the following requires more force/effort? A ...
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2answers
9k views

The most efficient Fan Blade Design [closed]

What could be the most efficient fan blade design? There are three main factors for a good fan: one is speed at which air is circulated; second,the volume of air it can circulate; and the third is ...
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2answers
74 views

Can you launch an item farther by slamming into it or accelerating it along a length

I am trying to desgin a little penny balista toy (built with a 3d printer). The short description is that there is a track with a mass ("hammer") that slides along it. There is a stack of pennies in ...
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1answer
1k views

Force in relation to stationary and non stationary objects

Say you have two situations with an object interacting with the ground. In the first situation the object has been sitting on the ground for a while so the force will be mg. In the second situation ...
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3k views

What is the difference between an accelerometer and an inclinometer?

When looking through papers for a controls project I found one that seemed to be referencing the fusing of sensor data from an inclinometer and an accelerometer. I always had thought that it was ...
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At what point does a projectile leave a slingshot?

Assuming a frictionless / "perfect" environment, and given a ball held in an elastic sling (like a hand-held catapult) where the pocket is lighter than the projectile itself, what is the point at ...
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958 views

Ropes and Pulleys - Really unintuitive answer

I usually don't want to do this, but please go to this link, the solution is too big to post it here http://engineering.union.edu/~curreyj/MER-201_files/Exam2_2_26_09_Solution.pdf And go to page 5 ...
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1answer
5k views

Can we determine the force an object exerts by its mass and acceleration?

I understand that the objects acceleration is determined by the force exerted on it, and that the force exerted on it is determined by its acceleration. But, does an object's (named A) acceleration ...
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109 views

Nonabelian gauge theories and range of the corresponding force

Do all nonabelian gauge theories produce short range force?
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6k views

What is the force exerted on a body that doesn't move?

If I push against a brick wall I'm exerting a force against the brick wall the the brick wall will exert the same force against me. These will cancel each other out and neither myself or the wall will ...
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1answer
3k views

Two problems with free body diagrams. Contradictions (solutions are provided)

This problem is similar, but also different question from my previous question. They are both unfortunately long. Problem/Solution #1 ! ! Quick Concept Check a) Could someone briefly explain to me ...
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2answers
432 views

Problem with forces acting upon a sloped plane

We have a structure that is sloped at 20 Degrees to the horizontal and weights 160N. We then have a force (wind) which is acting along the horizontal plane which has been calculated to be of about ...
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1answer
74 views

How to calculate torque required? [closed]

Here's my problem diagram: I am working on a hobby project in which a motor is required to rotate a pulley that is connected to a pendulum as shown in the image. The maximum torque, Horsepower and ...
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1answer
26 views

Stuck on a static equilibrium problem [closed]

This is the problem: "The figure below shows a 25-foot sailboat. The mast is a uniform 119-kg pole that is supported on the deck and held fore and aft by wires as shown. The tension in the forestay ...
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3answers
49 views

Work energy theorem: variation of kinetic energy as sum of terms given by the work of single forces

Work-energy theorem states that $$W_{\sum F_i}=\Delta K,$$ where I expressed with $W_{\sum F_i}$ the work done by the resultant of forces ${\sum F_i}$ and with $K$ the kinetic energy. In general it ...
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1answer
56 views

Work-energy theorem for a system

While studying energy conservation on Morin I found this explanation about the work-energy theorem for a system. The work–energy theorem stated before is relevant to one particle. What if we are ...
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1answer
40 views

Force with different distance dependence

Recently, I have learnt about the central force motion. I came across some forces with different distance dependence, for example, k/r^2(common) one, k/r^4, or even the combined one k/r^2 + k'/r^4 (k, ...
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1answer
72 views

Calculating force with two fulcrums and many forces [closed]

I may not be wording the question the right way. I have a lever. About 2/3 the way back there is a pivot point. We'll call this B On the very front (end of the lever) there is a block that the lever ...
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3answers
80 views

The force felt by a pilot when a package is dropped?

Here is a physics question that I wish to prove mathematically. A 100,000 kg aircraft drops a 1000 kg package of supplies over an arctic research station. What approximate force is felt by the 100 kg ...
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1answer
74 views

A cruise ship bumping against a lock gate [closed]

For my project, I need to create a lock gate which will be used for the Panama Canal. One of the many thing my teacher said, was that for the design of the lock gate, the gate should not fail when it ...
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1answer
78 views

How can the work done by friction be positive? [closed]

I have this energy related problem that i cannot understand in this problem, I am required to find the velocity of the 4.8kg mass when it hits the ground. I easily solved this problem using newton's ...
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1answer
37 views

Calculate final velocity for vertical projectile with air resistance

I am struggling to figure out how to calculate the final velocity of a projectile that is shot vertically upwards and then let fall down again to the starting point. I can easily calculate this in ...
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2answers
114 views

Is the work done by friction on an accelerating car zero?

Consider a car is accelerating and its tires are not slipping ,just rolling.what is the force on the car that changes its kinetic energy? Some people say in the definition of work dw=F.dx that dx is ...
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1answer
58 views

Homework Question: Moments [closed]

Can someone please explain this question? My work: If we take B to be the pivot then as B gets closer to mg the torque due to mg gets smaller, but I don't really see how this affects the force F (I ...
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1answer
47 views

Force felt by parachutist when opening the parachute [closed]

When falling down with air resistance, y-axis vertical (positive is up), x-axis is horizontal, we have that: $F_y=-mg-kv=ma_y$, where $k$ is the drag coefficient. Now if the man opens the parachute, ...
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4answers
89 views

Gravity and force

I have a question and am not able to answer it. Suppose you drop two objects from different heights. They are exactly the same shape, size and weight. Now we know that the gravitational acceleration ...
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1answer
88 views

Distance from Earth where gravity becomes negligible

This is a basic little problem I thought up when trying to remember some physics, and I wanted to see if it's at all correct: trying to figure out the distance from earth where gravity becomes ...
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1answer
54 views

What makes cart with a moving object in it gain speed (no friction anywhere)?

I would like to understand what makes the cart below the moving object move. There is no friction between any of the objects. The cart is moving therefore there is force applied to it. The only force ...
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1answer
35 views

Does the shape of a containter affect the apparent mass of liquid inside it when measured by a scale? [duplicate]

For both containers it is true that: $p_{bottom}=p_{atm}+\rho gh$ and $F_{bottom}=a*p_{bottom} \iff F_{bottom}=a*p_{atm} + a\rho gh$ I do not know how a scale functions, but I guess that the only ...
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4answers
119 views

Negative friction force, positive normal force

I realize that formulas don't always tell the whole story, but there seems to be some information missing from the equation: $F_f=\mu F_N$ Imagine we say up and right is positive. Then if an object ...
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1answer
45 views

Might one fall out of a basket swing?

My nieces like being pushed high in a basket swing. My sister-in-law worries they will fall out. Assuming I don't push them above horizontal, that I don't catch the basket and stop it mid-swing, and ...
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1answer
89 views

Newton's third law at the quantum level? [closed]

let's look at force at the atomic level to understand the newtons third law of motion. I'll use Helium atoms as an example. Now imagine we start with one atom HE2 stationary, and throw another atom ...
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3answers
90 views

If I walk forward and stop was there work done?

If I'm on a flat surface and I start walking and go to a constant velocity, then I slow myself back down to a stop, was there work done? I would think the answer is no because $work = force * ...
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1answer
78 views

Force (torque) to break a bike handlebar? [closed]

Few weeks ago a neighbor manage to hit my bike with his car while the bike was parked next to a wall, check the picture. One side of the handlebar was at the wall and the door of his truck hit ...
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1answer
29 views

How far will the key slide? [closed]

A person tosses his car keys on a shelf with an initial velocity of $2\:\mathrm{m/s}$. How far will the keys slide if the coefficient of kinetic friction between the surfaces is $0.3$? How would you ...
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1answer
66 views

Stacking compasses and what happens

A fellow science teacher had his compasses stacked on top of each other. He is teaching orienteering to his MO Science class. He noticed that they moved away from North and that each one would ...
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1answer
53 views

Water level in rotating glass [closed]

I have a glas with water in a train and the train is driving a curve (v and R given). How does the level of the water change? I know that I have the gravity and centripetal force, but how do I ...
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2answers
102 views

How does a cyclist moves the center of mass of the cycle-cyclist system?

Consider the image shown below, In the left diagram the centre of mass of the system lies upon the perpendicular from the point of contact. But in the right diagram the centre of mass has shifted ...
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3answers
122 views

Force of an object “skidding”?

Let's say I put the brakes on really suddenly in a car that was moving at 40mph. If I know how much force it takes to break the adhesion of the wheels, how do I find the force the car is exerting? ...
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1answer
113 views

A question on Newton's laws of motion [closed]

A force of $50N$ is required to push a car on a level road with constant velocity of $10m/s$. The mass of the car is $500kg$. What force should be applied to make the car accelerate at $1m/s^2$? I ...
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1answer
75 views

Work done by friction opposing a force at an angle

Let's imagine there's a block of mass m sitting on a rough surface with a kinetic friction coefficient $\mu$. It's being pulled with a constant force $A$ at $h$ degrees above the horizontal and is ...
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1answer
84 views

A heavy crate (mass m) is placed inside the flatbed of a truck but not tied down

A heavy crate (mass m) is placed inside the flatbed of a truck but not tied down. As the truck pulls away from a stop sign the crate remains in place and does not slide on the truck bed. What force ...
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2answers
49 views

Do we actually understand what the forces are?

I'm not being cheeky. I'm not looking for a mathematical explanation of how to measure forces. I'm trying to figure out if humans have yet to understand what is actually happening in the space ...