The best evidence that a substance's appearance can be significantly altered by both chemical and physical changes is the combination of examples 1 and 3.
Option A is correct.
What exactly is a change in the body?A substance undergoes a change in its physical characteristics when it undergoes a physical change. Most of the time, a physical change can be reversed. In the course of such a transformation, no chemical substance is produced.
What are two examples of physical and chemical changes?Chemical changes include processes like burning, frying, rusting, and rotting. The processes of melting, freezing, shredding, and boiling are all examples of physical modifications. The majority of physical symptoms can be reversed with enough energy.
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show answer no attempt 50% part (b) how much energy is lost to friction if the motorcycle only gains an altitude of 21 m before coming to rest?
From the information provided, the energy lost to friction if the motorcycle only gains an altitude of 21 m before coming to rest is approximately 65,954.64 J.
To calculate the energy lost to friction, we need to first determine the initial total mechanical energy of the motorcycle and the final total mechanical energy of the motorcycle after it has climbed to a height of 21 meters and come to rest. The difference between the initial and final energies will give us the energy lost to friction.
The initial total mechanical energy of the motorcycle is given by:
Ei = (1/2)mv² + mgh + 2(1/2)Iw²
where m is the mass of the motorcycle, v is its initial speed, h is the height it climbs, g is the acceleration due to gravity, I is the moment of inertia of the wheels, and w is their initial angular velocity.
We need to calculate the moment of inertia of each wheel:
I = (1/2)mr²
where m is the mass of the wheel and r is its radius. Substituting the given values, we get:
I = (1/2)(12 kg)(0.33 m)² = 0.6534 kg m²
The initial angular velocity of each wheel is not given, so we can assume that it is initially at rest (i.e., w = 0).
Substituting the given values into the equation for E, we get:
Ei = (1/2)(180 kg)(25 m/s)² + (180 kg)(9.81 m/s²)(36 m) + 2(1/2)(0.6534 kg m²)(0)²
= 101,812.44 J
The final total mechanical energy of the motorcycle is given by:
Ef = mgh
where m, g, and h are as before, and the speed and rotational energy of the wheels are both zero.
Substituting the given values, we get:
Ef = (180 kg)(9.81 m/s²)(21 m) = 35,857.8 J
The energy lost to friction is the difference between the initial and final energies:
Energy lost = Ei - Ef = 101,812.44 J - 35,857.8 J = 65,954.64 J
Question - Suppose a 180 kg motorcycle is heading toward a hill at aspeed of 25 m/s. The two wheels weigh 12 kg each and are each annular rings with an inner radius of 0.280 m and an outer radius of 0.330 m. Randomized Variables m 180 kg ˇ-25 m/s h 36 m. how much energy is lost to friction if the motorcycle only gains an altitude of 21 m before coming to rest?
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Which of these is constant for ALL types of electromagnetic radiation in a vacuum?
In a vacuum, the Velocity of ALL forms of electromagnetic radiation remains constant. In contrast to mechanical waves, electromagnetic waves may travel without a medium.
This indicates that electromagnetic waves are capable of passing not just through solid objects like air and rock but also through a vacuum like space.
At the speed of light (2.998 108 m/s), electromagnetic radiation is an electric and magnetic disturbance that travels through space. It moves in radiant energy packets called photons or quanta and has neither mass nor charge. X-rays, infrared, ultraviolet, gamma, and radio waves are all types of electromagnetic radiation. The sun and other celestial bodies, radioactive substances, and man-made gadgets are some examples of sources of EM radiation. EM displays both a wave and a particle nature.
The medium's electric and magnetic characteristics affect the velocity of electromagnetic waves.
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semiconductors can simplistically be thought of as an intermediate state between insulators and conductors. in a semiconductor, charges are normally bound in place (like in an insulator), but when injected with enough energy, the charges can move freely (like in a conductor). given what we have observed about the behavior of conductors and insulators in this exploration, what would happen if we replaced the pvc rod with a semiconductor material? what mechanisms could we employ to inject energy into the bound charges in the semiconductor to force it to act like more of a conductor?
Replacing PVC rod with semiconductor material, its behavior would depend on specific properties. To inject energy we can apply a voltage.
If we replaced the PVC rod with a semiconductor material, the behavior of the rod would depend on the specific properties of the semiconductor. Semiconductors have a unique property called the bandgap, which is the energy difference between the highest occupied energy level (valence band) and the lowest unoccupied energy level (conduction band). When an external energy source, such as heat or light, is applied to a semiconductor, it can promote electrons from the valence band to the conduction band, creating a flow of free electrons that can conduct electricity.
To inject energy into the bound charges in the semiconductor and force it to act more like a conductor, we could use several mechanisms. One common approach is to apply a voltage across the semiconductor, which creates an electric field that can promote electron movement. Another approach is to expose the semiconductor to light, which can excite electrons to higher energy levels and promote conduction. Additionally, thermal energy can cause the semiconductor to act more like a conductor by promoting electron movement. These mechanisms can be used to tailor the conductivity of semiconductors, which is the foundation of many modern technologies such as transistors, solar cells, and light-emitting diodes (LEDs).
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