 # Mechanics

## Mechanics is the branch of physics that deals with the interactions of objects and forces in the observable world. Questions asking about projectile motion, conservation of energy, and calculus based mechanics are perfect for this topic, but questions about repairs that a mechanic would do belong in our vehicles categories.

###### 5,270 Questions
Physics
Mechanics
Newtons Laws of Motion

# What is the formula for calculating acceleration?

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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Miscellaneous
Mechanics

# What is 90 Wt Gear Oil?

3 hrs

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Physics
Mechanics
Newtons Laws of Motion

# A simple net force definition?

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
Mechanics
Newtons Laws of Motion

# What is the resulting acceleration when a 300 N net force acts on an object with a mass of 3000 kilograms?

F=m*a

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

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Mechanics
Fluid Dynamics

# What is shock waves in fluid mechanics?

The speed of sound is constant in solids, liquids and gases. If something happens in such a medium the mechanical energy of it can propagate only at the speed of sound. If something is traveling through the medium faster than the speed of sound then it is pumping energy into a wave that contains more energy than what the simple passage of the object contains. This is the sonic boom hear by passing jet aircraft.

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Science
Mechanics
Newtons Laws of Motion

# If the coefficient of static friction is 0.3 how much more force is needed to lift the object than start it sliding?

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.

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Inventions
Physics
Mechanics

# Are there any MEMS gyro compass?

There are compass systems using MEMS.

MEMS means micro electromechanical systems. The MEMS compass system uses a vibrating structure gyroscope to operate. Most MEMS inertial navigation systems have integrated GPS. The very sophisticated ones are independent to prevent jamming, they use computers and an accelerometer as well as a MEMS gyroscope to operate.

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Science
Mechanics
Gravity

# Why does lubricant decrease friction?

The basic idea of friction is to fitting the ups and downs of one surface into the ups and downs of other surface. Mostly, we cannot see ups and downs of surfaces with our naked eye as it is in molecular level. This lubricant's molecules goes and fits in to the ups and downs of our required surface and makes surface smoother so that these ups and downs of other surface cannot fit into the required surface. Thus lubricant reduces the friction.

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Mechanics

# Is plutonium malleable?

Plutonium is a very strange material. Its malleability, volume, and brittleness all change, depending on its crystallographic phase (there are six at ambient pressure and a seventh under pressure).

The simplest answer is yes, plutonium is very malleable, but only in its delta phase.

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Mechanics
Gravity
Particle Physics

# Who first discovered neutron?

An English physicist named James Chadwick discovered the neutron- winning him a Nobel Prize in Physics in 1932.

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Mechanical Engineering
Mechanics

# What materials are used for making spanners?

The most common metals used for making spanners/wrenches are either Carbon Steel, Chrome Vanadium Alloy or Chrome Molybdenum Alloy.

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Mechanics
Physics

# Is there such a thing as a negative tension?

Negative tension can be considered the same as compression. It depends on the orientation you define your force vectors.

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Solid State Physics
Mechanics

# Why is it easier to push an empty box?

less friction

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Physics
Mechanics
Fluid Dynamics
Bombs and Explosive Materials

# What makes the whistling noise on bombs as they fall?

If you've ever seen a bomb you will notice that there are tail-fins. There are two purposes to these fins.

1. To make the bomb fall where it is intended to go. Hitting a target with a bomb is a hard thing to do and a lot of technology goes into making a bomb the right shape to 'fall straight.'
2. These tail-fins are also modified to make the screaming sound as they fall; to add a dimension of terror to a bombing raid.
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Mechanics

# Is centripetal acceleration a scalar?

acceleration is never a scalar...it describes in what direction is the motion of an object changing, so it can't be a scalar...

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Shopping
Mechanics

# Where can I buy a coilgun?

E-BAY!!!

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Physics
Mechanics
Construction Tools
Hand Tools

# Are pliers a wedge?

No, pliers are 2 levers working in together.

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Physics
Mechanics
Newtons Laws of Motion

# An object at rest will remain at rest and an object in straight-line motion will remain in straight-line motion unless acted upon by?

An unbalanced force.

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Physics
Mechanics

# Is the net force acting on an object always zero?

No because if it was, nothing would ever accelerate. If you apply a net force to an object, it accelerates. The net force acting on an object is always zero if and only if it is in static equilibrium; that is, the object is not moving (rotation or translation) or moving with constant velocity.

Given that an object is in static equilibrium, you can say that the net force and moments in all three cartesian directions are zero.

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Physics
Mechanics

# What is the physical significance of the thermal diffusivity and How is it defined and what?

Thermal diffusivity signifies the rate of heat transfer into the solid. If it is higher then less time is required for the heat to penetrate into the solid. it is th property of a solid. If we know the mass density,specific heat and thermal conductivity coefficient then we can determine its thermal diffusivity.

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Science
Physics
Mechanics

# The downward force of gravity and the upward force of air resistance on a ball?

The two forces acting opposite result in a terminal velocity. The terminal velocity is the fastest speed a falling object can attain.

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Physics
Space Travel and Exploration
Mechanics

# Give an example of uniform motion?

Uniform unaccelerated motion is the motion of a body that has constant velocity (same speed and direction all the time). So, any body moving without any force acting on it will have a uniform motion.

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Physics
Mechanics
Fluid Dynamics

# What do you call the curvature of a water surface in a glass tube?

The meniscus.

Related Information:

A meniscus can be concave or convex.

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Physics
Mechanics

# Why is friction important to road satey when it is wet?

Because a wet road has far less friction than a dry road. Friction is what is needed to accelerate the car, or turn, or stop the car. As the coefficient of friction decreases, the tires can't hold onto the road as well, meaning that they cannot push off the pavement to accelerate, they can't grab it as they try to stop, and they can't push off of it as the turn. The first simply means that you will spin your tires, it is the second two that are the big problem. If you can't stop, you'll probably crash into something, and if you can't turn, again, you'll probably crash into something, like somebodies living room.

It all boils down to the fact that all of these actions involve acceleration, with acceleration being like when you start from a stop, stopping is the same as acceleration, but opposite in direction, and turning involves accelerating in the new direction and decelerating in the original direction. As with all objects being accelerated, there is a force generated that is the result of mass (weight) and acceleration. Now, Newtons Third law of motion, states that when one body, in this case the wheels of the car, exerts a force on another object, that object exerts a force that is equal in strength, but opposite in direction. Thus, you impart a force on the road that is equal to the mass of your car, times your change in velocity, and this doesn't matter if you are starting, stopping, or turning, you will always impart this force on the earth and vice versa. Friction comes into play because, different surfaces, and the same surface under different conditions, have a different frictional coefficients, which is the threshold at which an object will remain on a surface and not just slide off of it. Water on the road changes this coefficient and makes it easy for your tires to lose their grip on the pavement.

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Physics
Science
Mechanics

# What does magnitude mean in Physics?

In physics, quantities can be subdivided into two groups: scalar quantities and vector quantities. A scalar quantity is a quantity with magnitude and a unit. A vector quantity is a quantity with magnitude, a unit, and a direction. Obviously, magnitude is required for both, but what exactly is magnitude?

Magnitude is simply the "size" of a quantity. Magnitudes are expressed in numerical form; e.g., 450, 0.45, 2/3, etc.

A common example of a scalar quantity is speed. If a man is driving at a speed of 50 km/h, we say the magnitude of the scalar quantity is 50. Notice that the sentence "I am driving 50" is incomplete. Therefore, the magnitude is equipped with a unit, in this case km/h (kilometres per hour).

A vector example is velocity, which is simply speed with a direction. If a plane is traveling at 240 m/s [East], then the magnitude of its velocity is 240 m/s, just like what the magnitude of its speed would be. But, since velocity is a vector, you must include the direction as well.

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