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:

The distance an object falls in free fall near the Earth’s surface, starting from rest, is calculated using the formula d = 12gt², where g is the acceleration due to gravity and t is the time elapsed. This formula comes from the kinematic equation for uniformly accelerated motion, where the initial velocity is zero, and it accounts for the constant acceleration of gravity acting on the object.

Correct Answer:

d = 1/2 gt²

Why Other Options Are Wrong:

d = vt

This is incorrect because this formula applies to motion at constant velocity, not accelerated motion. Free fall involves constant acceleration due to gravity, so the distance depends on the square of the time, not just the product of velocity and time.

d = gt

This is incorrect because it incorrectly treats the acceleration as a distance rather than incorporating the time squared factor. Distance under constant acceleration grows with the square of time, not linearly.

d = v²/2g

This is incorrect because this formula calculates the distance based on final velocity, not time. While it is derived from kinematic equations, it is not the standard formula for distance fallen as a function of time.

Explanation:

The energy equivalent of a mass is given by Einstein’s equation E=mc2E = mc^2. Energy is directly proportional to mass, so doubling the mass doubles the equivalent energy. If a 3 kg mass corresponds to 27 J, then a 6 kg mass would correspond to 27×2=5427 \times 2 = 54 J. This linear proportionality assumes the same constant of proportionality is used for both cases.

Correct Answer:

54 J

Why Other Options Are Wrong:

27 J

This is incorrect because it represents the energy of the original 3 kg mass, not the doubled 6 kg mass. Energy scales proportionally with mass.

81 J

This is incorrect because it overestimates the energy. Tripling the energy would require tripling the mass, not doubling it.

108 J

This is incorrect because it overestimates the energy by a factor of four. Doubling the mass only doubles the energy, not quadruples it.

Explanation:

Heat refers specifically to the transfer of energy between objects due to a temperature difference. It is energy in transit, not the energy contained within an object itself (which is internal energy) or a measure of temperature. When energy flows from a hot object to a colder one, that energy transfer is called heat.

Correct Answer:

the flow of energy resulting from a temperature difference.

Why Other Options Are Wrong:

the molecular motion inside of an object

This is incorrect because molecular motion relates to internal energy or kinetic energy of particles, not to heat, which is energy in transit.

a measure of how hot or cold an object is

This is incorrect because this describes temperature, not heat. Temperature is a scalar measure of thermal state, while heat is energy transfer.

the internal energy of an object

This is incorrect because internal energy is the total energy stored within an object’s molecules, whereas heat specifically refers to energy moving between objects due to temperature differences.

Explanation:

The distance fallen under constant acceleration from rest is given by d = 12gt2. Substituting g = 9.8 m/s² and t =10 s:

d = 12(9.8)(102) = 0.5*9.8*100 = 490m

The mass of the object does not affect the distance fallen when air resistance is negligible, so any mass will fall the same distance.

Correct Answer:

490.0 m

Why Other Options Are Wrong:

49.0 m

This is incorrect because it is 1/10 of the correct distance. The calculation must include t², not just multiply by t.

98.0 m

This is incorrect because it represents g × t, which would be the distance if acceleration were 1 m/s² or if incorrectly using the formula d = gt.

245.0 m

This is incorrect because it represents half of the correct distance, likely due to a miscalculation of 12gt2. The correct value accounts for g = 9.8 and t² =100.

Explanation:

When light passes from a less dense medium (air) to a denser medium (water), it bends toward the normal due to a decrease in speed. According to Snell’s law, n₁sin⁡θ₁ = n₂sin⁡θ₂, where n₂>n₁ (water is denser than air), the refracted angle θ₂ will be smaller than the incident angle θ₁. Therefore, for an incident angle of 30° in air, the refracted angle in water will be less than 30°.

Correct Answer:

Less than 30°.

Why Other Options Are Wrong:

Greater than 30°

This is incorrect because light bends toward the normal when entering a denser medium, resulting in a smaller refracted angle, not a larger one.

Equal to 30°

This is incorrect because the speed of light changes between air and water, causing refraction. The angle cannot remain the same unless the media have identical refractive indices.

Dependent on the temperature of the water

This is incorrect because, although temperature can slightly affect water’s refractive index, the primary factor determining the refracted angle is the ratio of the refractive indices of air and water. The temperature effect is negligible for basic refraction calculations.

Explanation:

Nuclear fusion is the process in which lighter atomic nuclei combine to form a heavier nucleus, releasing energy. This occurs naturally in the sun, where hydrogen nuclei fuse to form helium. In contrast, nuclear reactors typically rely on nuclear fission, the splitting of heavy atoms such as uranium or plutonium. Therefore, fusion is exemplified by the process in stars, not by fission in reactors.

Correct Answer:

the process of hydrogen combing to form helium on the sun

Why Other Options Are Wrong:

the process that produces energy in a nuclear reactor

This is incorrect because most nuclear reactors use fission, not fusion. Fission splits heavy nuclei to release energy, whereas fusion combines light nuclei.

the splitting of a uranium atom into atoms of barium and krypton

This is incorrect because this describes nuclear fission, not fusion. Fusion combines nuclei, while fission splits them.

all of the above are examples of nuclear fusion

This is incorrect because only hydrogen fusion in stars is true nuclear fusion; the other processes are fission or energy generation methods.

Explanation:

A blue shift occurs when the wavelength of light from an object decreases, indicating that the object is moving toward the observer. The greater the blue shift, the higher the speed of approach. Therefore, a celestial object with a significant blue shift is moving toward the Earth at a high speed.

Correct Answer:

the object is moving towards the Earth at a high speed

Why Other Options Are Wrong:

the object is moving away from the Earth at high speed

This is incorrect because motion away from Earth causes a red shift, not a blue shift. A blue shift indicates approach, not recession.

the object is moving away from the Earth at a slow to moderate speed

This is incorrect because, again, any motion away would produce a red shift. Blue shift cannot indicate recession.

the object is moving towards the Earth at a slow to moderate speed

This is incorrect because the question states the spectrum is blue shifted to a great extent, indicating a high speed, not a slow to moderate speed.

nothing about the object's velocity

This is incorrect because the blue shift directly provides information about the object’s radial velocity relative to Earth. The extent of the shift allows astronomers to determine speed.

Explanation:

In a perfectly elastic collision between two identical masses moving in opposite directions at equal speeds, they exchange velocities while conserving both momentum and kinetic energy. Since the masses are equal and speeds are equal, after the collision, each mass continues moving with the same speed but in the opposite direction to its original motion. This is a direct consequence of the symmetry and conservation laws in elastic collisions.

Correct Answer:

equal in magnitude but opposite in direction to their original velocities

Why Other Options Are Wrong:

less in magnitude and opposite in direction to their original velocities.

This is incorrect because in a perfectly elastic collision between equal masses, the speeds remain unchanged; only the direction changes.

Zero

This is incorrect because both masses do not stop; momentum and kinetic energy are conserved, so they continue moving.

equal to original velocities

This is incorrect because “equal to original velocities” implies they continue in the same direction as before, which violates momentum conservation in an opposite-direction collision.

less in magnitude and in same direction as their original velocities

This is incorrect because after an elastic collision, the direction of motion is reversed for equal masses moving head-on, and the magnitude of velocity remains unchanged.