Answer: B. Concrete
Explanation:
Let N = reacting force pressing the bodies in context together (units in Newtons),
The question stated that the force pressing the two mounted/stacked objects together is equal to the weight of the object on top.
We need to start by finding the weight of the piece of wood.
friction is given by
f = μN
The value of f is 22.5,
and from the chart reference the coefficient of friction between wood and stone, μ is 0.30.
22.5 = 75. 0.30
Putting the values into the equation: 22.5 = 0.30N.
Divide both sides by 0.30 to find the value of N:
N= 22.5/0.3 = 75
Now that the piece of wood will be placed on another surface, its weight of 75 Newton is the force pressing the two bodies together.
To determine the new surface, you should find the new coefficient of friction by using the new value of the force of friction given 46.5:
46.5 = µ(75).
Divide both sides by 75 to isolate μ.
The refer chart also indicates that the coefficient of friction equals 0.62 between wood and concrete, so the new surface corresponding to 0.62 is the concrete, which is (B).
Answer:
Oscillation whose amplitude reduce with time are called damped oscillation. This happen because of the friction. In oscillation if its amplitude doesn't change with time then they are called Undamped oscillation
Explanation:What is centripetal acceleration?
Can an object accelerate if it's moving with constant speed? Yup! Many people find this counter-intuitive at first because they forget that changes in the direction of motion of an object—even if the object is maintaining a constant speed—still count as acceleration.
Acceleration is a change in velocity, either in its magnitude—i.e., speed—or in its direction, or both. In uniform circular motion, the direction of the velocity changes constantly, so there is always an associated acceleration, even though the speed might be constant. You experience this acceleration yourself when you turn a corner in your car—if you hold the wheel steady during a turn and move at constant speed, you are in uniform circular motion. What you notice is a sideways acceleration because you and the car are changing direction. The sharper the curve and the greater your speed, the more noticeable this acceleration will become. In this section we'll examine the direction and magnitude of that acceleration.
The figure below shows an object moving in a circular path at constant speed. The direction of the instantaneous velocity is shown at two points along the path. Acceleration is in the direction of the change in velocity, which points directly toward the center of rotation—the center of the circular path. This direction is shown with the vector diagram in the figure. We call the acceleration of an object moving in uniform circular motion—resulting from a net external force—the centripetal acceleration
a
c
a
c
a, start subscript, c, end subscript; centripetal means “toward the center” or “center seeking”.
Answer:
In the scientific model, electric current is the overall movement of charged particles in one direction. The cause of this movement is an energy source like a battery, which pushes the charged particles. The charged particles can move only when there is a complete conducting pathway (called a ‘circuit’ or ‘loop’) from one terminal of the battery to the other.
A simple electric circuit can consist of a battery (or other energy source), a light bulb (or other device that uses energy), and conducting wires that connect the two terminals of the battery to the two ends of the light bulb. In the scientific model for this kind of simple circuit, the moving charged particles, which are already present in the wires and in the light bulb filament, are electrons.
Electrons are negatively charged. The battery pushes the electrons in the circuit away from its negative terminal and pulls them towards the positive terminal (see the focus idea Electrostatics – a non contact force). Any individual electron only moves a short distance. (These ideas are further elaborated in the focus idea Making sense of voltage). While the actual direction of the electron movement is from the negative to the positive terminals of the battery, for historical reasons it is usual to describe the direction of the current as being from the positive to the negative terminal (the so-called ‘conventional current’).
The energy of a battery is stored as chemical energy (see the focus idea Energy transformations). When it is connected to a complete circuit, electrons move and energy is transferred from the battery to the components of the circuit. Most energy is transferred to the light globe (or other energy user) where it is transformed to heat and light or some other form of energy (such as sound in iPods). A very small amount is transformed into heat in the connecting wires.
The voltage of a battery tells us how much energy it provides to the circuit components. It also tells us something about how hard a battery pushes the electrons in a circuit: the greater the voltage, the greater is the push (see the focus idea Using energy).
Explanation:
