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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.
2,416 Questions
What is the difference between homogeneous and heterogeneous mixture?
A homogeneous mixture is a substance that is uniform in composition. Solutions are examples of homogeneous mixtures.
A heterogeneous mixture is a mixture in which the composition is easily identified, as there are two or more phases present. Suspensions are examples of heterogeneous mixtures.
Particle size distinguishes homogeneous solutions from other heterogeneous mixtures. Solutions have particles which are the size of atoms or molecules - too small to be seen.
In contrast a suspension is a heterogeneous mixture of larger particles. These particles are visible and will settle out on standing.
Corn oil, white vinegar a saturated sugar solution is homogeneous since only a colorless liquid is observed. Air with no dust is also a homogeneous.
Beach sand is heterogeneous since you can see different colored particles. Vinegar and oil salad dressing is heterogeneous since two liquid layers are present, as well as solids. Air with clouds is heterogeneous, as the clouds contain tiny droplets of liquid water.
What is the difference between homogeneous and heterogeneous mixtures?
Homogeneous is a single phase mixture that means we observe only one state and material shows same properties on all of its part while heterogeneous material consists of at least two phases that means two different visible states.
A zero force member is a structural member within a truss that is not subject to any force due to the geometry and external loading conditions. These members do not affect the overall stability or load-carrying capacity of the truss structure and can be identified and removed to simplify the analysis of the truss.
What is the coefficient of friction in a 6 inch round duct with a velocity of 200cfm?
The coefficient of friction for air flow in a round duct is typically around 0.02. This coefficient may vary depending on factors such as surface roughness and airflow conditions.
What force allows work to be done?
Any force can produce work if it causes displacement. If displacement is in opposite direction of force, work done will be negative and if displacement is in direction of force work done will be positive. If there is no displacement, work done is zero. Eg: Gravitational force pulls you down towards earth, in pulling you down it does work on you which gets stored in form of potential energy.
Energy for A+
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. There are several types of friction: Dry friction is a force that opposes the relative lateral motion of two solid surfaces in contact.
Two circular objects of different sizes that rotate together is a wheel and axle. Inclined plane wrapped around a central cylinder or bar to form a spiral is a screw.
Is a pencil sharpener a first class lever?
no it is in fact a first class lever because a see-saw is first class and this is basically a see saw except instead of a handle on each side there is 2 on one side so therefore its a first class but people think it is a second class because of scissors but this a scissors have a difference and that difference it that when using scissors when you move one handle, it moves on the other side of the fulcrum but with a can opener the handles make the actual metal that opens the can move not just the same thing but on the other side
What is the value of absorption coefficient of an open window?
Open doors and windows are considered to be completely absorptive (a=1) because all the sound waves continue traveling out the space instead of being reflective back into the room.
It should be noted that for the case of doors or windows opening into a space where another wall may reflect the sound (hallway, closet, etc.) then the absorption will be less than ideal, but still fairly significant.
What are liquid drops or solid particles spread through gas?
A gas cannot easily pass through a liquid or a solid however it can be entrapped in it . If a gas bubble is formed in a liquid it moves upward and escapes out of the liquid. Gas cannot pass through a solid barrier.
What is the formula for conservation of mechanical energy?
There are many equations to solve for energy, depending on what form of energy your looking at. For kinetic energy, us KE = (1/2)mv2 where KE is kinetic energy, m is mass, and v is velocity. For potential energy used PE=mgh where PE is potential energy, m is mass, g is gravity, and h is height. Mechanical energy is PE + KE. There are also numerous equations for finding the amount of thermal energy.
What type of force does an object have if its net force is equal to zero?
If the net force on an object is zero, we can say that the forces are balanced, or that they are in equilibrium(which really means the same thing). There may be forces acting on the object, but there is an equal and opposite force pushing or pulling in the opposite direction, and all the forces balance out. Alternatively, there may be no forces acting on the object at all.
It will stretch 6 cm.
What is an object's mass multiplied by its velocity?
mass x velocity = momentum.
(velocity = speed with a direction)
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.
What level of a lever is a bottle opener in?
Answer #1:
It is a third class lever.
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Answer #2:
It is a second class lever.
the answer is "m" but do not get it confused with "M" because that is a different term
What amount of force is needed to bend metal?
Depends on what metal you are refering to. * Aluminum is can be bent at 1 ton * Stainless at 50 ton * Mild Steel at 100 tons * Carbon Steel can be bent at 150 tons. All of these metal depend on the thickness of the material. For example, the thickness of these metal would have to be between the thickness of .25 (quarter inch) to .50 (half inch). Note: It also depends of the quality of the metal. SS 1311-00 steel (Swedish standard), for example, can handle 220N per square millimetre until it reaches its yield point. Once the yield point is passed some fraction of the deformation will be permanent and non-reversible. Answer: Mathematically
Δ = PL3/(48EI) Where: Δ = deflection
L = span
E = Modulus of Elasticity (see link for typicals)
I = Moment of Inertia
b = width
d = depth
I = bd3/12 for a rectangular cross section
Do all objects accelerate the same when they are dropped?
If we are to neglect air resistance, then yes. There is a video of the Apollo 15 astronauts putting this to the test on the moon, using a feather and a hammer. When the astronaut drops the objects, they hit the ground at the same time. The video is on YouTube.
If a stone falls from rest and takes 16 seconds to hit the ground How tall is the ledge?
The use of more accurate figures for gravity (a) will affect the answer, as does the figure of 16 seconds which limits the significant figures of the answer.
For a = 9.8 m/sec2, the result is 1.3 x 103 meters.
For a = 9.80665 m/sec2, the result is 1255.2512 meters.
First Calculation
Using the equation
s = ut +1/2at2
Where s = displacement, u = initial velocity, a = acceleration & t = time.
Since
u = 0, t = 16s & a = 9.80665 ms2
s = (0 * 16) + (1/2 * 9.8 * 162)
s = 0 + 1255.2512
s = 1255.2512 meters
Second Calculation
First, we must assume that there is negligible air resistance. This is questionable because by analysis, one can see that the stone will be traveling quickly by the time it approaches the ground. However, it is necessary because we do not know any of the characteristics of the stone (dimensions/mass), nor the fluid resistance constant of the air.
Using a common kinematics formula, it is them possible to find the height of the ledge. Note that since the stone falls (rather than being thrown, or the like) it has an initial velocity of zero. The acceleration due to gravity used is 9.8m/s2. A rounded version of the constant is used because the question does not state whereabouts this ledge is, and acceleration due to gravity changes slightly based on where one is.
d=Vit+(1/2)*at2
d=0+(1/2)*(9.8m/s2)(16s)2
d=1254.4m
Considering significant figures, the height of the ledge is 1.2x103m.
Third Calculation
Assuming that air resistance is negligible, the ledge is 1254.4 meters tall.
Use the kinematics equation x = 0.5at2 + v0t + x0
where a stands for acceleration, t for time, v0 for initial velocity, and x0 for initial position.
We are given that v0 = 0. We can also say that the top of the ledge is x0 and that x0 = 0. Furthermore since we assumed that the only force acting on the stone is gravity, gravity is the force that will provide the acceleration. Thus, a = g = 9.8m/s2.
Putting this all together we get x = 0.5(9. 8m/s2)(16 sec)2 + (0)(16 sec) + 0 = 1254.4 m.
Note that if you are using significant figures the answer will be 1.3 x 103 m.
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It depends on the direction of the two forces. If the two forces are in the same direction, the net force would be 60N or -60N. If the two forces are in opposite directions the net force would be either 30N or -30N.
Are you supposed to torque bolts or nuts?
It depends on the application, if you are speaking generally.
If you meant for applications where the bolt and nut are both present, and specific torque specifications are required, it really doesn't matter. Whichever is best accessible by the torque wrench. The only stipulation is that whichever item the torque wrench is not being used on, must be static (unable to turn). For example, if you are torquing the nut, the bolt must not be able to turn (held in place with a wrench, if necessary) while the torque wrench is being read, for a reading to be accurate.
Can an object's velocity change direction when its acceleration is constant?
No. Acceleration is a change of velocity and doesn't have to point in the same direction. Consider braking car: it still moves with decreasing velocity in one direction, while braking force and thus acceleration is in the opposing direction.
