Physics

Mechanics

Newtons Laws of Motion

Acceleration

There are a few. The most famous is a = F/m, where F is the net force applied to a mass, m.

Acceleration is also the change in velocity, (Delta-V), divided by the change in time, (Delta-t). So, a =Î”v/Î”t.

For example, if an object's velocity changes from 10 meters per second to 20 meters per second in five seconds, its acceleration is (20-10)/5 = 2 meters per second per second, or 2 meters per second squared (m/s2).

For circular motion, centripetal acceleration is v2/r, where v is the linear velocity of the rotating object and r is the radius of its circular path.

Equations in a nutshell

Constant Accelerationa = Î”v/Î”t = (vfinal - vinitial) / (tfinal - tinitial)a = (v2-u2)/2s

a = 2(s - ut)/t2

where

a=acceleration (m/s2)

v=final velocity (m/s)

u=initial velocity (m/s)

t=time (s)

s=distance (m).

OR

a=(v-vo)/t

a=acceleration (m/s2)

v=final velocity (m/s)

vo=initial velocity (m/s)

t=time (s).

Newton's Second Law

F = ma, thus, a = F/m

Centripetal Acceleration

ac = v2/r

Warning: Calculus Speak:

Acceleration is the second derivative of position with respect to time: d2x / dt2, which makes it the first derivative of velocity: dv / dt. Therefore, the acceleration is the slope of the curve on the velocity-versus-time graph.

Thus:

a = dv / dt = d2x / dt2

Acceleration is a quaternion with real and vector parts:

a= (V^2/R - cDel.v)) + (dcv/dR + cDelxv + V^2/R r)

a= (V^2/R - cV/R cos(v)) + (dv/dt + cv/R sin(v) + V^2/R r)

where R=ct and dR=cdt.

cv/Rcos(v) is the Centrifugal Acceleration a part of the real accelerations in the first parenthesis. The second parenthesis contains the vector accelerations.

Acceleration = F/m, where F is the net force applied to a mass, m.

a=f/m,

acceleration in terms of velocity.

a = v - u/t Delta Velocity divided by Time.

A = Î”V Ã· T Acceleration is worked out by (final speed - initial speed)/ time taken for change in speed a = v2-v1/ t2-t1 Strictly you should say velocity ie the speed in a certain direction. Youalso have the formula f=ma which tells you that the force needed to get something moving will be the mass of the object multiplied by the accelertion you want to achieve; so from this formula if you know force and mass you can work out acceleration. The formula for acceleration is: Vf-(Vi)/t ie. change in velocity per unit time. Instantaneous acceleration in its differential form is d2x/dt2 where x is a function of time t.

Acceleration is the time rate of change of velocity.

That is, acceleration =dv/dt (v - velocity ; t - time)

Or simply acceleration = change in velocity / time

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Physics

Mechanics

Newtons Laws of Motion

A net force is a measure of the force being exerted on an object; zero net force means an object is at rest or moving at a constant speed.

Definition of net force:

The net force on an object is the vector sum of all individual forces acting on it.

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Physics

Newtons Laws of Motion

Force and mass

331332333

Science

Fossil Fuels

Newtons Laws of Motion

There are many examples, depending upon the use. Most often, liquid fuel is described as an option as compared to solid fuel.

Rockets are one example where both solid and liquid fuels may be used. Liquid hydrogen is the common rocket liquid fuel.

Cooking stoves can use solid or liquid fuel, in addition to gas. The most common cooking stove liquid fuel is alcohol.

329330331

Science

Physics

Newtons Laws of Motion

Angular velocity just means how fast it's rotating.

If youaa want more angular velocity, just rotate it faster or decrease the radius (move it closer to the center of rotation).

Just like force = rate of change of momentum, you have torque= rate of change of angular moment

Or

We can increase the angular velocity of a rotating particle by applying a tangential force(i.e. accelaration) on the particle.

Since the velocity of the particle is tangential with the circle along which it is moving, the tangential accelaration will not change the diriction of the velocity(as angle is 0),but will cause a change in magnitude. Thus angular velocity will increase.

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Physics

Mechanics

Newtons Laws of Motion

F=m*a

a=F/m = 300N/3000kg=0.1m/s^2

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Physics

Isaac Newton

Newtons Laws of Motion

Mass and acceleration. Force = mass x acceleration

317318319

Physics

Isaac Newton

Newtons Laws of Motion

It means there is no net force acting on it.

A plane in the air has no acceleration, but it does have forces acting on it.

Lift pushes it up

Gravity pushes it down

Air resistance opposes its movement

Thrust provides movement

When all these forces are equal the plane will move at a constant velocity. If one of these forces becomes greater the NET force on the plane will no longer be 0 and there will be an acceleration or deceleration.

Hope that helps.

Another example would be space as there are no opposing forces, if in space once a speed was that speed would be constant until you 1.) decelerated with a force in the opposite direction 2.) accelerated the speed past your current velocity in your current direction 3.) Get caught by some planets gravity and crash to you death (but then this question is the least of your problems)

293294295

Science

Physics

Newtons Laws of Motion

If friction is negligible, then it requires force only to start an object moving, but no force

to keep it moving. You could barely touch it, so that it just begins to creep imperceptibly,

and then back off completely ... if friction is negligible, the object keeps going. It doesn't

take more force to move an object farther, and it doesn'ttake more force to move a heavier

object, if friction is negligible.

Where friction is negligible, force causes an object to accelerate. When the force is removed,

the object continues moving at a constant speed.

Where friction is negligible, you can push on the object as hard or as lightly as you want ...

the harder you push, the greater its acceleration will be, and the greater the speed will be

when you stop pushing. Also, you can keep up the force through as long or as short a distance

as you want, before you stop pushing.

The product of (force) times (distance) is the energy you put into the object. When you quit

pushing, all of that energy you gave the object will show up as the object's kinetic energy.

It will be equal to (1/2 x the object's mass) times (its speed).

The quantities are all up to you.

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Science

Mechanics

Newtons Laws of Motion

for lifting the object there is no role of friction,but of air friction.since no info,. is given about it so air friction = 0.thereby for lifting we have mg = mass * 9.8 (the wight of the object). and for sliding we have 0.3*mg . therefore 0.7mg of more force is required to lift it.

303304305

Newtons Laws of Motion

Gravity

Use the formula v2=u2+2*a*s

v=final velocity

u=intital velocity

a=acceleration due to gravity

s=displacement

This then gives:

2*9.8*5

=98

square root of 98

9.89ms-1

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Fluid Dynamics

Newtons Laws of Motion

Upthrust is the upward or buoyant force acting on an object in a liquid. It is a force, and so has the units of force. This is pounds in the imperial system, and Newtons in the SI.

281282283

Physics

Isaac Newton

Newtons Laws of Motion

F = M A

A = F / M = 180/60 = 3 meters per second2

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Physics

Isaac Newton

Newtons Laws of Motion

The larger the objects mass the larger the inertia and also the gravitational force.

259260261

Newtons Laws of Motion

In normal walking, it should be about equal to your weight spread over the square area of contact with the ground. Hence an 80 kg man with a 100 cm2 footprint would exert 0.8 kg/cm2 where a woman with a smaller footprint due to shoe design might exert twice this force.

251252253

Isaac Newton

Newtons Laws of Motion

the first law is:

An object at rest stays at rest and an object in motion stays in motion unless acted on by an outside force

so all of them.

-in golf, the golf ball will move when hit and stop only when gravity and friction make it happen.

in this case the ball is at rest on the tee and will not move until struck by the club (acting as ouside force 1), at which poin it then flies out until the friction of the air and gravity's pull force it back down to the earth, at which point friction with the ground is then added which all conspire to slow the ball to a stop.

-in foot ball, the players run with the ball until tackled by another player.

in this case the two players are the opposing forces

-in baseball the ball is thrown is moves toward the catcher until either the bat strickes it and it is sent elsewhere, or the catcher catches it and throws it back to the pitcher.

in this case the ball is the object and the bat and pitcher are the outside forces acting on the ball to give it motion.

257258259

Science

Physics

Chemistry

Newtons Laws of Motion

Force: A push or pull on an object.

true

456

Physics

Asteroids

Newtons Laws of Motion

the gravity of large masses. the large masses could be other planets or stars or our sun

Their own momentum. other masses only deflect them by changing their momentum.

211212213

Kinematics

Newtons Laws of Motion

Gravity

At the Earth's surface the nominal value is about 9.8 m/s2. The exact value varies from place to place.

187188189

Physics

Isaac Newton

Newtons Laws of Motion

F=ma

a=F/m

a=7500/1500

a=5m/s^2

345

Physics

Mechanics

Newtons Laws of Motion

An unbalanced force.

345

Miscellaneous

Physics

Newtons Laws of Motion

Well Mass is a big boy now and he wears his pull-up training pants so he doesn't have too many accidents. But Inertia..well unless you stop her from going she just keeps going.

181182183

Physics

Isaac Newton

Newtons Laws of Motion

Newton's second law states that an object will change acceleration if pushed or pulled upon. An example would be pushing a ball, the velocity goes from 0 to how hard you push the ball. Newton's second law also states that if it gets twice the mass it accelerates half as much. An example would be pushing a 10 lb ball as hard as you can, then pushing a 5 lb ball as hard as you can. The 10 lb ball would accelerate less than the 5 lb ball because the 10 lb ball has more mass.

Newton's second law is related to unbalanced forces. Hence they should be a net force for application of Newton's Second Law of Motion. If you push a ball then it will not move initially due to the force of friction. Once you push harder and your force is more than the force of friction then the ball will start moving. The amount of acceleration of the ball is related by F = ma. Hence more mass means less acceleration. Similarly more force means more acceleration.

777879

Physics

Math and Arithmetic

Science Experiments

Newtons Laws of Motion

Fundamental properties you can directly measure in physics:

- Volume
- Weight
- Conductivity/Resistance
- Malleability
- Color
- State change temperatures (freezing/melting, boiling)

Density, an important property, is not directly measured, as it is calculted based on mass per unit volume.

Fundamental properties in physics (well, mechanics anyway, let's not delve into particle physics) are mass, distance, duration, and electric charge. But electric charge is not measured directly, it is calculated from other measurements, and its units defined through electric current.

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Units of Measure

Physics

Statics

Newtons Laws of Motion

Advantages of Friction

In some situations, friction is very important and beneficial. There are many things that you could not do without the force of friction.

- Walking: You could not walk without the friction between your shoes and the ground. As you try to step forward, you push your foot backward. Friction holds your shoe to the ground, allowing you to walk.
- Writing: Writing with a pencil requires friction. You could not hold a pencil in your hand without friction. It would slip out when you tried to hold it to write. A pencil eraser uses friction to rub off mistakes written in pencil lead. Rubbing the eraser on the lead wears out the eraser due to friction, while the particles worn off gather up the pencil lead from the paper.

- Driving car: Your car would not start moving if it wasn't for the friction of the tires against the street. With no friction, the tires would just spin. Likewise, you could not stop without the friction of the brakes and the tires.
- Friction Pen: Inventors have invented useful items like the friction pen/highlighter. You are able to erase the pen/highlighter mark. The problem is that the rubber at the back gets dirty easily.
- There wouldn't be a Universe without friction.

Disadvantages of Friction

Friction can cause problems or be a nuisance that you try to minimize.

- Makes movement difficult: Any time you want to move an object, friction can make the job more difficult. Excess friction can make it difficult to slide a box across the floor, ride a bicycle or walk through deep snow. An automobile would not move forward very well unless its friction was not reduced. Oil is needed to lubricate the engine and allow its parts to move easily. Oil and ball bearings are also used in the wheels, so they will turn with little friction.
- Wastes energy: In any type of vehicles as a car, boat or airplane--excess friction means that extra fuel must be used to power the vehicle. In other words, fuel or energy is being wasted because of the friction. Fluid friction or air resistance can greatly reduce the gas mileage in an automobile.
- Heats parts: The Law of Conservation of Energy states that the amount of energy remains constant. Thus, the energy that is "lost" to friction in trying to move an object is really turned to heat energy. You've seen how people will try to start a fire by vigorously rubbing two sticks together. Or perhaps you've seen an automobile spin its wheels so much that the tires start to smoke. These are examples of friction creating heat energy. Just rub your hands together to create the same effect. Besides the problem of losing energy to heat, there is also the threat of a part overheating due to friction. This can cause damage to a machine.
- Wears things out: Any device that has moving parts can wear out rapidly due to friction. Lubrication is used not only to allow parts to move easier but also to prevent them from wearing out. Some other examples of materials wearing out due to friction include the soles of your shoes and a pencil eraser.
- Carpet burn is because of friction.

Compromise

A compromise is needed between too much friction and not enough.

For example, if you wanted to slide a heavy box across the floor, you would want to reduce the friction between the box and the floor, so that it would be easy to move. Lubrication of some sort is often a way to reduce friction.

Friction is necessary in many applications to prevent slipping or sliding. But also, it can be a nuisance because it can hinder motion. A good compromise is necessary to get just enough friction or a proper combination of frictions

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