PHYS 2102 C876 Conceptual Physics

Explanation:

When a bar magnet is broken into smaller pieces, each piece forms its own north and south pole. This occurs because the magnetic domains within the material, which are regions of aligned atomic magnetic moments, remain aligned in each fragment. Therefore, every piece becomes a complete magnet with both poles, regardless of how many times it is divided. The phenomenon demonstrates that magnetic monopoles do not exist in isolation; magnetic poles always appear in north-south pairs.

Correct Answer:

Each piece becomes a magnet with a north and south pole

Why Other Options Are Wrong:

The pieces lose their magnetic properties

This is incorrect because breaking a magnet does not destroy its magnetic domains. Each fragment retains the alignment of its domains and therefore continues to act as a magnet with both poles.

Only the ends of the original magnet retain their poles

This is incorrect because all pieces, not just the original ends, form new north and south poles. Magnetic poles are not limited to the ends of the original magnet.

The poles of the original magnet are unchanged

This is incorrect because breaking the magnet creates new poles in each fragment. The original poles are not preserved in isolation; they become distributed across the smaller pieces.

Explanation:

Power is defined as the rate at which work is done or energy is transferred. Mathematically, it is expressed as P = Wt, where W is work and tt is the time taken. This definition emphasizes that power measures how quickly work is performed, not the total amount of work itself.

Correct Answer:

Power is the rate at which work is done.

Why Other Options Are Wrong:

Power is the total amount of work done.

This is incorrect because total work measures energy transferred, but power specifically measures how fast that work is done, not the cumulative amount.

Power is the force applied over a distance.

This is incorrect because force applied over a distance defines work, not power. Power involves the additional factor of time.

Power is the energy transferred over time.

This is partially correct in concept, but the more precise definition is that power is the rate of doing work. While energy transferred over time can describe power, the standard definition in physics emphasizes work done per unit time.

Explanation:

The principle of conservation of momentum states that in the absence of external forces, the total momentum of a system remains constant. When the ice-skater catches the ball, the momentum of the ball is transferred to the skater, causing the skater to move. However, the total momentum of the ice-skater and ball system remains the same before and after the catch. Momentum is redistributed within the system, but no external forces act to change the system’s total momentum.

Correct Answer:

The momentum of the system remains constant before and after the catch.

Why Other Options Are Wrong:

The momentum of the system increases as the ball is caught.

This is incorrect because momentum cannot increase without an external force. The system’s total momentum is conserved, not increased.

The momentum of the system decreases as the ice-skater moves backward.

This is incorrect because the system is isolated; momentum does not decrease. The skater’s backward movement is simply a redistribution of momentum between the skater and the ball.

The momentum of the system is transferred entirely to the ice-skater.

This is incorrect because the momentum is shared between the ice-skater and the ball; the total system momentum remains unchanged, not entirely concentrated in the skater.

Explanation:

Sound travels as a mechanical wave through the vibration of particles in a medium. In solids, particles are closely packed and strongly bonded, which allows vibrations to be transmitted more efficiently from one particle to the next. This close molecular arrangement enables sound to travel faster in solids than in liquids or gases, where particles are more spread out and interactions are weaker.

Correct Answer:

Solids have more closely packed molecules, allowing faster energy transfer.

Why Other Options Are Wrong:

Gases have higher temperatures, which increases sound speed

This is incorrect because while higher temperature can increase sound speed in gases, it is still much slower than in solids due to the lower density and weaker particle interactions in gases.

Liquids are denser than solids, making sound travel faster

This is incorrect because density alone does not determine sound speed; elasticity of the medium also matters. Solids are both more elastic and dense, which allows faster propagation than liquids.

Sound cannot travel in solids, only in liquids and gases

This is incorrect because sound requires a medium, and solids are excellent conductors of sound. In fact, sound travels fastest in solids.

Explanation:

Induction is the process by which a neutral object acquires a charge due to the influence of a nearby charged object without direct contact. The electric field from the charged object causes the redistribution of charges within the neutral object, creating regions of positive and negative charge. This allows the neutral object to become polarized or even obtain a net charge if grounded, all without physically touching the charged object.

Correct Answer:

Induction

Why Other Options Are Wrong:

Conduction

This is incorrect because conduction requires direct contact between a charged object and a neutral object to transfer charge.

Convection

This is incorrect because convection refers to the transfer of heat through fluid motion, not the transfer of electrical charge.

Insulation

This is incorrect because insulation refers to materials that resist the flow of electric charge, and does not describe the process of charging an object.

Explanation:

Gravitational force between two masses decreases as the distance between them increases. This relationship is described by Newton’s law of universal gravitation, which states that the gravitational force FF is proportional to the product of the two masses m₁ and m₂ and inversely proportional to the square of the distance rr between them: F = Gm1m2r2. This is known as the inverse square law, meaning that if the distance between two objects doubles, the gravitational force becomes one-fourth of its original value. The principle highlights the strong dependence of gravitational force on distance.

Correct Answer:

Gravitational force decreases with increasing distance according to the inverse square law.

Why Other Options Are Wrong:

Gravitational force is independent of distance and only depends on mass.

This is incorrect because gravitational force depends not only on mass but also on the distance between the masses. Ignoring distance contradicts the inverse square law.

Gravitational force increases with distance due to mass attraction.

This is incorrect because gravitational force weakens with increasing distance, not strengthens. The force is strongest when objects are closest.

Gravitational force is only relevant in a vacuum.

This is incorrect because gravitational force acts in all environments, not just in a vacuum. Air or other media do not negate gravitational attraction.

Explanation:

For an object in uniform circular motion, the centripetal force F_c is related to mass m, speed v, and radius r by the formula F_c= mv2r. Rearranging for speed: v = FCrm. Substituting the given values: v = 5.5*0.651.0 = 3.575 ≈ 1.89 m/s. The speed is closest to 2.0 m/s.

Correct Answer:

2.0 m/s

Why Other Options Are Wrong:

1.5 m/s

This is incorrect because it underestimates the speed calculated using the centripetal force equation. The correct calculation yields approximately 1.89 m/s.

2.5 m/s

This is incorrect because it overestimates the speed. Using the given force, mass, and radius, the speed cannot reach 2.5 m/s.

3.0 m/s

This is incorrect because this speed significantly exceeds the value determined from the centripetal force formula. The correct speed is lower due to the given force and mass.

Explanation:

Water in a pressurized tank has potential energy primarily because of the pressure and, in some cases, its elevated position relative to a reference point. Potential energy is the energy stored in an object due to its position or configuration. In a pressurized tank, the force exerted by the pressurized water represents stored energy that can be converted into kinetic energy when the water is released. The higher the pressure and/or elevation, the greater the potential energy, which is why pressurized tanks are used for water distribution and other energy-related applications.

Correct Answer:

It is stored under pressure, which increases its potential energy due to its elevated position.

Why Other Options Are Wrong:

It is moving rapidly, which contributes to its kinetic energy.

This is incorrect because kinetic energy depends on the motion of the water, not its stored position or pressure. The question specifically asks about potential energy, which is separate from the energy due to movement.

It is heated, which increases its thermal energy.

This is incorrect because thermal energy arises from the temperature of the water, not the mechanical energy stored due to pressure or position. While heating can increase internal energy, it does not contribute to gravitational or pressure-related potential energy.

It is in a state of equilibrium, which means it has no energy.

This is incorrect because being in equilibrium does not eliminate the energy stored in the system. A pressurized tank at equilibrium still contains potential energy due to the pressurized water and its elevation. Equilibrium simply means forces are balanced, not that energy is absent.

Explanation:

The distance traveled by a freely falling object from rest can be calculated using the equation of motion s = 12gt2, where gg is the acceleration due to gravity (approximately 10 m/s²) and t is the time. Substituting the values: s= 12*10*52= 5 × 25 =125 meters. Therefore, the rock falls a distance of 125 meters in 5 seconds.

Correct Answer:

125m

Why Other Options Are Wrong:

100m

This is incorrect because it underestimates the distance. Using s = 12gt2 with t = 5s and g = 10 m/s², the correct calculation yields 125 meters, not 100 meters.

145m

This is incorrect because it overestimates the distance. The formula shows that the rock falls 125 meters, so 145 meters is too large for a 5-second fall under standard gravity.

200m

This is incorrect because it is significantly higher than the calculated distance. For an object in free fall from rest, 5 seconds under g =10 m/s² cannot result in a 200-meter fall.