PHYS 2102 C876 Conceptual Physics

Explanation:

In the absence of significant external forces such as gravity or friction, an object in motion will continue to move at a constant velocity in a straight line according to Newton’s First Law of Motion (the law of inertia). In outer space, there is negligible air resistance and no significant gravitational influences, so once the astronaut throws the rock, it will continue in motion indefinitely at the same speed and direction. There is no mechanism for the rock to "lose its steam" or for inertia to be "used up."

Correct Answer:

Continue in motion with the same speed and direction

Why Other Options Are Wrong:

Eventually stop since all objects ultimately "lose their steam"

This is incorrect because objects do not naturally lose momentum or energy without an external force acting on them. In the vacuum of space, there is essentially no friction or resistive force to slow the rock down.

Eventually stop as its inertia slowly becomes used up

This is incorrect because inertia is not something that is "used up." Inertia is an inherent property of mass that resists changes in motion, so it does not decrease over time. The rock’s motion will continue unless acted upon by an external force.

Either of the above..depending on whether the astronaut continues to push it

This is incorrect because after the initial throw, the astronaut is no longer applying a force. The rock’s motion is independent of further pushes, so it will continue indefinitely in its original motion regardless of subsequent action.

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:

A diesel truck operates using a heat engine, specifically an internal combustion engine. In this system, chemical energy stored in diesel fuel is released through combustion inside the engine’s cylinders, producing high-temperature and high-pressure gases. These gases expand and push pistons, converting thermal energy into mechanical energy that drives the truck’s wheels. This process is based on the basic principle of a heat engine: converting heat energy into useful mechanical work.

Correct Answer:

It uses combustion to generate heat, which is then converted into mechanical energy.

Why Other Options Are Wrong:

It converts electrical energy into kinetic energy.

This is incorrect because a diesel truck does not rely on stored electrical energy to produce motion. Its primary energy source is chemical energy in fuel.

It relies on wind energy to move.

This is incorrect because diesel trucks do not harness wind energy. They are powered by combustion within the engine.

It stores energy in batteries for propulsion.

This is incorrect because diesel trucks use fuel combustion, not battery storage, to generate mechanical work. Batteries are relevant in electric vehicles, not conventional diesel engines.

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:

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:

In circular motion, the force that keeps an object moving along a curved path and directed toward the center of the circle is called the centripetal force. This force is necessary to continuously change the direction of the object’s velocity, ensuring it follows a circular trajectory. Without this inward-directed force, the object would move in a straight line due to inertia.

Correct Answer:

Centripetal force

Why Other Options Are Wrong:

Centrifugal force

This is incorrect because centrifugal force is a fictitious force that appears to act outward on an object in a rotating reference frame. It is not a real force acting toward the center, which is required for circular motion.

Gravitational force

This is incorrect because gravitational force acts between masses and is only one type of force that could provide centripetal acceleration in specific cases (like planets orbiting the sun). It is not the general term for the force toward the center of any circular motion.

Frictional force

This is incorrect because friction is only sometimes the source of centripetal force (such as a car turning on a road). The general term for the inward force in circular motion is centripetal force, not friction.

Explanation:

When a bar magnet is broken in half, each resulting piece forms a smaller magnet that still has both a north and a south pole. Magnetic monopoles do not exist in practice, so it is impossible to isolate a single north or south pole. The magnetic domains in each half realign to produce complete north and south poles, preserving the magnetic properties of the original magnet.

Correct Answer:

becomes two bar magnets with two poles

Why Other Options Are Wrong:

contains one magnetic pole

This is incorrect because isolated magnetic poles (monopoles) do not exist in normal materials. Each fragment always has both a north and south pole.

becomes unmagnetized

This is incorrect because breaking a magnet does not remove its magnetism. Each piece retains magnetic properties and forms a complete dipole.

reverse magnetic polarity

This is incorrect because the polarity of each fragment does not flip when broken. Each piece maintains the same relative north and south orientation as the original magnet.

Explanation:

According to Faraday’s law of electromagnetic induction, the induced voltage (emf) in a loop is proportional to the rate of change of magnetic flux through the loop. Rotating the loop faster increases the rate at which the magnetic flux changes, thereby increasing the induced voltage. Therefore, as the rotation speed increases, the magnitude of the induced voltage also increases proportionally.

Correct Answer:

The induced voltage would increase.

Why Other Options Are Wrong:

The induced voltage would decrease.

This is incorrect because increasing rotation speed increases the rate of change of flux, which increases, not decreases, the induced voltage.

The induced voltage would remain constant.

This is incorrect because the induced voltage depends on how quickly the loop rotates; faster rotation leads to greater emf.

The induced voltage would become zero.

This is incorrect because zero induced voltage occurs only if there is no change in magnetic flux, which is not the case when the loop is rotating.

Explanation:

Hydrogen nuclei (protons) naturally repel each other due to their positive charges. The force preventing them from coming together is the repulsive electrical (electrostatic) force. To achieve nuclear fusion, the protons must be moving fast enough to overcome this repulsion so that the strong nuclear force, which binds nucleons together, can take over and hold them together in a fused nucleus.

Correct Answer:

repulsive electrical

Why Other Options Are Wrong:

strong nuclear

This is incorrect because the strong nuclear force is what actually binds nucleons together once they are close enough. It is not the force that needs to be overcome to initiate fusion; rather, it is the attractive force that enables fusion once repulsion is overcome.

strong gravitational

This is incorrect because the gravitational force between protons is negligibly small compared to the electrostatic repulsion. Gravity does not play a significant role in overcoming proton repulsion for fusion at atomic scales.

attractive magnetic

This is incorrect because magnetic forces are irrelevant in overcoming the repulsion between hydrogen nuclei. Fusion depends on electrostatic and nuclear forces, not magnetism.