Mechanics

no because work = force x distance

The length of an arc, of radius L (which is the length of the pendulum) and angle Φ is LΦ cm.

So L*0.9 = 18 ie L = 20 cm

Smaller the number, bigger the size. 14 guage is bigger.

Potential energy can be calculated by the equation U ( which is the potential energy) = mgh, where m is hte mass, g is gravity, and h is the height of the object above the point where h=0 (often the ground). So, as long as h does not equal zero (imagine the man sandin on a cliff above sea leve, which is h=0) then he will have potential energy.

Angular momentum is defined as the cross product of a distance (from the axis of rotation) and a momentum, so you have to use units accordingly. In the SI, that would be meters x kilograms x meters / second, which you can simplify to meters squared x kilograms / second. This is equivalent to joules x seconds.

Simply put, sounds are made through vibrations in the air. We can translate these vibrations into sound because of our ear drums.

To find the average velocity of a projectile, use V = D/T (Velocity equals Displacement over Time).

As a result of friction, kinetic energy is commonly lost; the result is heat energy.

Mostly , but transparent plastic is also used.

This is a really good question. Speed and velocity are similar. Velocity is just speed, but a direction is included. Say you are driving a car. Driving forward is positive velocity, while driving backwards is negative velocity. Speed is what a radar gun would show about the car either way, because it can't tell if the car is moving forward or backward. Therefore, you can have negative velocity, but there is no such thing as negative speed. A speed graph will always stay positive, while a velocity graph can go negative at some places, though it doesn't have to. HOPE THIS HELPS!!!

Addendum: Only in ONE-dimensional motion can "Velocity vs Time" graphs be truly drawn; as only in this dimension can direction be indicated by +/- sign. In 2-D and 3-D motion, the graph equivalent must be "Speed vs Time" because these graphs do not indicate direction.

It's hard to guess that in advance, though as a general rule you can guess that smooth surfaces have a lower coefficient of friction than rough surfaces, and lubrication usually reduces the friction. However, to get more precise information, this has to be measured. Of course, you can first search the Internet - somebody may already have measured it.

An inertial reference frame is a frame ... a box, a laboratory, a space capsule etc. ... in which Netwon's laws of motion hold true.

Example: My office on the earth is not an inertial reference frame. An object in motion doesn't "remain in constant uniform motion without application of an external force", because of air resistance. Also, an object released in the middle of the air doesn't stay there, it accelerates toward the floor.

Graphical methods involve examining charts, pictures, and graphs to determine the answer to a problem. This would be used when finding the solution to a system of equations and graphing all the equations to find points at which they coincide.

Analytical methods involve calculating answers without the use of charts or graphs. If one were to solve a system of equations by substitution, this would be an example of an analytically produced solution

25 Nm (Newton-meters) is a unit of torque that measures the rotational force applied at a distance of one meter from the axis of rotation. It indicates the amount of twisting force that can be exerted, which is crucial in applications like tightening bolts or turning screws. A higher torque value means more force is applied, making it easier to rotate or move an object. In practical terms, 25 Nm is often used in automotive and mechanical contexts to specify the required tightness for various components.

If you drop them at the same time, they will land at the same time. Also the branch will move up as the weight is released and will oscillate depending on how heavy the objects were. Be carefull, you might fall from the sudden motion.

Yes but make sure you are clear in your understanding between the coefficient of friction and the force of friction. The force of friction is the force that resists the motion of two surfaces moving against one another. The amount of friction is determined by the product of the coefficient of friction and the normal (perpendicular) force that is pressing the two surfaces together. The coefficient of friction is a unit-less constant, that indicates how two surfaces compare to two other surfaces that are being pressed together the same amount. If the normal force is the same on two pairs of surfaces the pair of surfaces with the lowest coefficient of friction will experience the lower force of friction.

All materials carry sound. The harder the better usually. In rooms that need to be sound-proof, the whole room is suspended from the building structure.

Commonly, thermics may refer to any of several physical topics involving heat. It has also been used as a synonym for thermodynamics, but is only rarely used in this way today.

Zero is.

You didn't give me any values, but I can give you a formula that will answer your question. The force exerted by a spring is given as F = -KX, where K is the spring constant and x is the distance the spring is compressed or stretched. When the spring is compressed fully, it has a force F. When the spring is at equilibrium(aka not stretched), it has a force of zero. We can average these to say that the Average force of a spring is F = 1/2 -KX. We can now substitute the -1/2 KX into the equation F = ma. This yeilds -1/2 KX = ma. Solve for acceleration, we get (-1/2 KX)/m = a. Multiply this quantity by the amount of time the spring pushed on the object, and you have your velocity. Hope this helps whoever asked. --An AP Physics Student Bored in Study Hall

Beats are caused by the interaction of two waves with different periods. The Waves crests do not line up every oscillation, but when they do, they have a much larger than normal crest, which results in an observable beat.

Applied force, if someone is chopping the rock with an axe or hammer.

No. It's an example of a Second Class lever.