Classical Mechanics: Newton's Laws and Energy

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Questions and Answers

A car accelerates from rest to 20 m/s in 5 seconds. If the car's mass is 1500 kg, what is the net force acting on it, according to Newton's second law?

6000 N

A gas is compressed adiabatically. What happens to its temperature and why?

The temperature increases because no heat is exchanged with the surroundings, and the work done on the gas increases its internal energy.

Two objects, A and B, are in thermal equilibrium. Object A has a higher temperature than object B. Is this possible? Explain briefly.

No, this is not possible. Thermal equilibrium implies that two objects in contact have reached the same temperature; there is no net heat flow between them.

Describe the relationship between electric potential and electric field.

Electric field is the negative gradient of electric potential. In simpler terms, the electric field points in the direction of the steepest decrease in electric potential. Signup and view all the answers

A ball is thrown upwards. Describe the energy transformations that occur from the moment it leaves the hand until it reaches its maximum height.

As the ball leaves the hand, it has kinetic energy. As it rises, kinetic energy is converted into gravitational potential energy. At maximum height, all kinetic energy has been converted to potential energy (momentarily, before it falls back down). Signup and view all the answers

Explain why, according to the second law of thermodynamics, a broken glass will not spontaneously reassemble itself.

The second law of thermodynamics states that the entropy (disorder) of an isolated system tends to increase. A broken glass reassembling itself would require a decrease in entropy, which is statistically highly improbable and violates the second law. Signup and view all the answers

A positively charged particle moves into a region with a uniform magnetic field. If its velocity is perpendicular to the magnetic field, describe the particle's subsequent motion.

The particle will move in a circular path because the magnetic force is always perpendicular to the velocity, causing a centripetal acceleration. Signup and view all the answers

A box is pushed across a floor with a force of 50 N over a distance of 10 meters. If the coefficient of kinetic friction between the box and the floor is 0.2 and the box weighs 200 N, determine the net work done on the box.

100 J Signup and view all the answers

Explain how the principle of wave-particle duality applies to electrons and what experimental evidence supports this concept.

Wave-particle duality suggests that particles, like electrons, can exhibit both wave-like and particle-like properties. The double-slit experiment with electrons demonstrates this, where electrons create an interference pattern (wave-like behavior) even when sent through the slits one at a time (particle-like behavior). Signup and view all the answers

Describe the phenomenon of quantum entanglement and explain why it does not violate the principle that information cannot travel faster than light.

Quantum entanglement is when two or more particles become linked, and their fates are intertwined regardless of the distance separating them. Measuring the state of one particle instantaneously influences the state of the other. It doesn't violate special relativity because while the correlation is instant, you can't use it to send a classical message faster than light. Signup and view all the answers

Explain the concept of time dilation in special relativity and provide a real-world example where time dilation is a significant factor.

Time dilation is the slowing down of time for an object in motion relative to a stationary observer. A real-world example is the Global Positioning System (GPS), where time dilation effects due to the satellites' high velocities and weaker gravitational field must be accounted for to ensure accurate positioning. Signup and view all the answers

Describe how gravitational lensing works and what it reveals about the distribution of mass in the universe.

Gravitational lensing occurs when the gravity of a massive object, like a galaxy or black hole, bends and magnifies the light from objects behind it. This phenomenon reveals the presence and distribution of mass, including dark matter, as the amount of bending depends on the mass of the lensing object. Signup and view all the answers

Explain the difference between nuclear fission and nuclear fusion, including the conditions required for each process and an example of where each occurs.

Nuclear fission is the splitting of a heavy nucleus into lighter nuclei, requiring a critical mass and often neutron bombardment, as seen in nuclear reactors. Nuclear fusion is the combining of light nuclei into a heavier nucleus, requiring extremely high temperatures and pressures, as occurs in the core of the Sun. Signup and view all the answers

Describe the significance of the Cosmic Microwave Background (CMB) radiation and what it tells us about the early universe.

The Cosmic Microwave Background (CMB) is the afterglow of the Big Bang, representing the earliest light emitted when the universe became transparent. It provides a snapshot of the universe about 380,000 years after the Big Bang, revealing information about its temperature, composition, and early structure. Signup and view all the answers

Explain the role of dark matter and dark energy in the current understanding of the universe's composition and expansion.

Dark matter makes up about 27% of the universe and provides the extra gravitational pull needed to explain the observed motions of galaxies and galaxy clusters. Dark energy makes up about 68% of the universe and is responsible for the accelerating expansion of the universe, acting as a repulsive force. Signup and view all the answers

How do lenses use refraction to form images, and what is the difference between a converging and diverging lens?

Lenses use refraction to bend light rays and form an image where the rays converge. A converging lens, like a convex lens, bends light rays inward to focus them at a point. A diverging lens, like a concave lens, bends light rays outward, making them appear to come from a point. Signup and view all the answers

What is the relationship between mass and energy as described by Einstein's famous equation, $E=mc^2$, and what are some practical implications of this relationship?

Einstein's equation, $E=mc^2$, states that energy (E) and mass (m) are equivalent and can be converted into each other, with $c^2$ representing the speed of light squared. This relationship implies that a small amount of mass can be converted into a tremendous amount of energy, as demonstrated in nuclear reactions and atomic weapons. Signup and view all the answers

State Heisenberg's uncertainty principle, and explain its implications for measuring the position and momentum of a particle.

Heisenberg's uncertainty principle states that it is impossible to simultaneously know the exact position and momentum of a particle. The more accurately you know one, the less accurately you know the other. Mathematically, it says that the product of the uncertainties in position ($\Delta x$) and momentum ($\Delta p$) is greater than or equal to a constant ($\hbar/2$): $\Delta x \Delta p \geq \frac{\hbar}{2}$ Signup and view all the answers

Flashcards

What is Physics?

Study of matter, energy, and fundamental forces governing the universe.

Classical Mechanics

Deals with the motion of macroscopic objects under forces.

Newton's First Law

Object at rest stays at rest; object in motion stays in motion (constant velocity) unless acted upon by a force.