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    I Conservation of KE, wedge striking ball

    So assume we have a wedge traveling at a constant V horizontally, that is braced so it CANNOT move vertically. Ignore air and friction. See picture. It hits a stationary tennis ball and due to the angle, there is a net force on the ball as shown. The energy should come from the kinetic...
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    I How is static friction the centripetal force during a car turning?

    Hello, as you can see i am trying to understand conceptually how the tires during turning create a centripetal force. It was explained to me that as we turn the car tires, the tires similar to a ski or a wedge, now want to push the ground to the side and forward. If the ground was loose, this...
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    What makes a door move, the torque or the force or both?

    I have seen an example of a horizontal beam on a hinge. Beam of length L acted on my gravity MG at center, where the hinge supplies 1/4MG force to the door. Therefore there is a net torque, causing angular acceleration and a net force, causing translation about the center of mass. Maybe it is...
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    Angular momentum of an object about its axis is equal to that of a parallel axis?

    Take for example earth. Earth has angular momentum about its own axis. However, if we ignore the orbital portion, the angular momentum of the earth relative to the sun's axis is the same. Another example is the spinning bike wheel/person holding it in a chair. It has angular momentum about its...
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    Does Newton's Third law apply to torque/rotation?

    For example, lets say i have force acting on an object about some pivot. That object will apply an equal force about the same pivot, at equal lever arm, back. So there it seems like if the forces are in line, acting on the same pivot point, there is an equal and opposite torque. However, if i...
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    Spinning Bike Wheel Example, how is angular momentum conserved?

    In the classic example of a person holding a spinning bike wheel, as they flip the wheel over, angular momentum is conserved by the person/chair spinning with 2x the angular momentum of the initial wheel. Not questioning that. However, I thought ang momentum is always conserved about a...
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    Torque Balance of Motor and Transmission

    I read this in my college design book, that for a car transmission, if the engine provide T, and the output is RT(ratio x Torque), the difference of (RT-T) must be back on the engine mounting. This example makes sense, I am not questioning that. However, if i have an offset gear drive, like...
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    Reaction Torque from an Ice Auger

    Trying to determine the reaction torque a person would have to supply to keep the auger head from spinning when the ice auger is drilling a hole So I am an ice fisherman and I got thinking, when you drill a hole with an ice auger, the head always wants to turn opposite of the auger bit. You have...
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    Rotational Work versus Linear Work

    In the link below, there is a force tangent to a wheel that travels distance Ds. There is also a torque that moved thru an angle. Why do they consider them equal? There are two works, shouldn't they be added together...
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    Angular momentum conserved with multiple gears?

    Say we have a motor attached to the earth with gear A, that drives identically sized gear B. Gear B spins on its own axis and but is also attached to ground. Torque between gears is equal. Technically each gear has equal but opposite AM right, but If I take earth into account, how is Ang...
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    Conservation of Angular Mometum for a Car/Earth System

    See attached. You can see how the car as a whole conserves angular momentum with earth. Car pushes back, earth moves back and rotates, car accelerates forward. https://www.animations.physics.unsw.edu.au/jw/momentum.html However, the ground puts a friction force on the front non-driving wheel...
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    Equal and Opposite Torques

    Okay, I asked this post(below) the other day on how ang. momentum was conserved by the ball. The answer was the ball receives an equal torque back from the door...
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    Ball hits a pivoting rod, what torque changes the angular momentum of the ball?

    Okay, i know that as a ball collides with a pivoting rod on an axis, the ball has angular momentum. Therefore after the collision, the ball is stopped or slowed, and the rod swings. The ball provides a force and torque to the rod. But if I isolate the ball, isn't the only thing acting on the...
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    I Why don't we consider Earth's forces/movement in problems?

    According to N3L, every time we move or apply forces, there is a reaction. Therefore, walking, driving and stopping would all affect earth right? Then why don't we have to consider that in our physics problems? Wouldn't falling down to earths surface mean earth was moving towards us too, so...
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    Conservation of energy given the Earth's rotation?

    So earth and everything is spinning around at 1000mph at the equator. From our perspective we are at a standstill. But let's say a fighter jets flies east to West against earth at same speed, so now relative to someone in space, the earth spins but the plane is at a standstill. Wouldn't that...
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    Is there any work done by static friction when accelerating a car?

    I'm asking for clarification, but it's my understanding, that of the thread below, and my college physics book Paul A tipler, that when walking or driving a car, the force of friction from the ground does no work. This makes sense in a car becuase the engine/fuel makes the power, driving the...
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    Opposing force of the axle when a torque is applied to a wheel?

    Okay lets say we have a wheel attached to a fixed axle, free to spin, ignore friction and we apply a force on the edge of the wheel. That force creates a torque, does the axle have an opposing force to keep the wheel/axle assembly from accelerating linearly? Ive learned on this forum that when...
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    How can we say we do work in walking up stairs or similar?

    I see physics problems asking one to calculate the work done in climbing stairs. However, isn't the system the person, and isn't the person not having any external work done? Then how can we say they did work? Now I know when climbing or raising an object, work=mgh=potential energy. But if the...
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    Power delivered/Internal work done by a car's engine

    Attached is an example from my Tipler physics book of a determining the power delivered from a cars engine. I get the derivation(math), but am having some issues with the understanding/concept. Mainly, isn't Power=Work done/time. If so, they define the system as Car-earth. There is no external...
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    How does static friction propel a car forward given a torque applied to the wheels?

    Ok so please bear with me here and what is almost certainly a really stupid question, partly because I don't quite know how to ask it. When you have a wheel such as one attached to a car, a torque is applied to it from the engine. It's my understanding that the wheel would slide over the road...
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    Friction ON wheels (say a car driving or accelerating)

    I know it takes friction for a car/wheels to move forward. However, I am confused by the free body diagram. As a torque is applied to the wheel, the wheel applies a force to the road, and as a reaction, the road puts a force on the wheel(this is friction). Then wouldn't the torque of friction...
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    Static friction's role in walking

    Okay, I have been reading when we walk, it is the static friction that propels us forward. See below: "When we start running we exert a force on the ground. That's why ground also gives us a reaction force equal and opposite to the force exerted by us. The horizontal component of that reaction...
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    What slows an object during collision, force or loss of energy?

    I have an example from my machinery handbook which shows the kinetic energy of a pile driver and shows it will drive a pile some distance at a force until the energy is expended. The formula is (Average force of blow times distance)= Weight of object (driver) times distance it falls) Just...
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    Help -- I don't understand work

    Work is basically energy applied thru a force to move an object right? Or another way put it is just force thru a displacement, which can be thought of as "energy used" I see definitions saying it is a transfer of energy, not sure why they mean by that
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    What happens to energy when work is done?

    Okay say I have an object with kinetic energy and it collides with a stationary object. The moving object does work. Work means energy spent thru a force and distance right? So my question is once the energy gets used, does the moving object stop becuase it has no energy. Or is it stopped...
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    Elastic Collision: how do the forces and work done make sense?

    Okay, say we have two balls(equal mass and size), 1 and 2. #1 has kinetic energy and #2 is at a standstill, they collide. Ignore all friction, heat, sound losses etc.. Now I know that 1 exerts a force on 2, hence doing work, which in turn uses its kinetic energy up. Therefore, 2 speeds up...
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    Confused about work concepts

    Okay, I am confused about work and what it is. I know the formula, W=FDCos(theta), so putting it in math terms doesn't help. I am trying to get a layman's/physical understanding of it. Everything I read says it is equal to energy, so then I think it must be energy right, has same units? But...
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    Confused about pressure

    Summary: Trying to understand pressure and it's relation to force Okay here is my dumb thought. A force is defined as an influence on an object, causing change in motion correct? Then how can pressure be a force on an area? Maybe I'm stuck on the word "on". But the way I'm reading the force...
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    I Is mass the same as matter?

    No I'm not dumb, just confused. I keep reading that mass is the amount of matter. So is a 1kg mass matter? Is mass the stuff made of things . So when we say 1kg are we talking about the material? Or is mass the measure of how much? Looking for basic help. I always think about mass as how much...
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    Force and rate of change of momentum

    My question is simply..if force does equate to the rate of change of momentum, then why is it not taughted as this rate rather simply a push or pull? Is it becuase really they are the same thing and it is much easy to explain/work with? Just curious Guess up until now I didn't even think of...
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