Preap Physics Final Exam

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A vector is a physical quantity that has both magnitude and direction. Magnitude refers to the size or quantity of the vector, while direction indicates the orientation or the way it is pointed. Vectors are commonly used to represent various physical quantities such as displacement, velocity, force, and acceleration. They are represented by an arrow, where the length of the arrow represents the magnitude and the direction of the arrow represents the direction of the vector. Scalars, on the other hand, only have magnitude and do not have a specific direction associated with them. Resultant refers to the sum or combination of multiple vectors. A frame of reference is a coordinate system used to describe the position and motion of objects.

The graph on the right illustrates that the acceleration is not constant, as it is shown to change over time. The graph shows different values of acceleration at different points, indicating that the acceleration varies.

Centripetal force is the correct answer because it is the force that acts towards the center of a circular path, causing an object to move in that path. This force is necessary to keep an object moving in a curved trajectory and prevents it from moving in a straight line. Centripetal force is always directed inward and is responsible for maintaining the object's circular motion.

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In this situation, the delivery person is lifting the carton vertically upward, which represents a positive displacement along the y-axis. The other options do not involve a vertical upward displacement of the carton.

The law of universal gravitation states that two objects always exert gravitational forces on each other. This means that any two objects in the universe will attract each other with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. Therefore, option a is correct. Additionally, the force of gravity does depend on the mass and the distance between the two objects, as explained by the law of universal gravitation. Therefore, option b is also correct. Hence, the correct answer is d. both a and b.

When two ice skaters initially at rest push off one another, their final momenta are equal in magnitude and opposite in direction. This is because of the law of conservation of momentum, which states that the total momentum of an isolated system remains constant. Since the skaters are initially at rest, their total momentum is zero. When they push off each other, their momenta change, but the total momentum of the system must still be zero. Therefore, their final momenta must be equal in magnitude but in opposite directions to cancel out each other and maintain the total momentum of the system at zero.

Electric force and gravitational force are alike in that both forces are field forces. This means that they can act on objects even when they are not in direct contact with each other. Both forces can act over a distance, with the electric force acting between charged particles and the gravitational force acting between objects with mass. These forces create fields in their respective domains, which allow them to exert their influence on other objects without direct contact.

When the net force acting on a car is zero, it means that the forces acting in opposite directions cancel each other out, resulting in no overall force. In this situation, the car maintains both its speed and direction because there is no external force acting on it to change either of these factors.

At the top of its path, the ball experiences zero velocity because it momentarily stops moving before it starts to fall back down. At the same time, it experiences non-zero acceleration due to the force of gravity pulling it downwards. This acceleration is responsible for changing the ball's velocity from zero to a non-zero value as it starts to fall.

When a hammer drives a nail into a piece of wood, the action-reaction pair is that the hammer exerts a force on the nail, and in return, the nail exerts an equal and opposite force on the hammer. This is in accordance with Newton's third law of motion, which states that for every action, there is an equal and opposite reaction.

The distance between two compressions of a longitudinal wave is referred to as the wavelength. In a longitudinal wave, the particles of the medium vibrate back and forth in the same direction as the wave is traveling. The compressions are the regions where the particles are closest together, and the wavelength is the distance between two consecutive compressions. The amplitude refers to the maximum displacement of the particles from their equilibrium position, the frequency is the number of complete cycles of the wave that occur in one second, and the trough is the region where the particles are farthest apart.

The correct answer is b. Kinetic energy involves motion, and potential energy involves position. This is because kinetic energy is the energy of an object due to its motion, while potential energy is the energy that an object possesses due to its position or condition. Kinetic energy is dependent on the mass and velocity of an object, while potential energy is dependent on factors such as height, position, and elasticity. Therefore, the main difference between the two is that kinetic energy is associated with motion, while potential energy is associated with position.

According to Hooke's law, the force exerted by a spring on an object is proportional to the displacement of the spring. This means that as the spring is stretched or compressed, the force it exerts on the object increases or decreases accordingly. The mass of the object, length of the spring, and volume of the object do not directly affect the force exerted by the spring, making option b the correct answer.

The motion of a projectile in free fall is characterized by a constant horizontal velocity (vx = constant) because there is no horizontal acceleration. The vertical acceleration is always equal to the acceleration due to gravity (ay = -g) because the only force acting on the projectile in the vertical direction is gravity. The vertical velocity (vy) changes over time due to the acceleration, so it is not constant. Therefore, option c is the correct answer.

In a perfectly inelastic collision, two objects stick together and move with a common velocity after colliding. This means that they combine and become one object after the collision. In this type of collision, kinetic energy is not conserved, and some or all of the initial kinetic energy is converted into other forms of energy, such as heat or sound. Therefore, the correct answer is d. perfectly inelastic.

The given observation indicates that the first rod repels the glass rod rubbed with silk, which is known to have a positive charge. This suggests that the first rod must also have a positive charge, as like charges repel each other. Additionally, the first rod attracts the rubber rod rubbed with fur, which is known to have a negative charge. This further supports the conclusion that the first rod has a positive charge, as opposite charges attract each other. Therefore, the correct answer is a. Positive.

Momentum is defined as the product of mass and velocity. Therefore, if the velocities are the same, the object with less mass will have less momentum. This is because momentum is directly proportional to mass.

In an elastic collision, kinetic energy is always conserved. This means that the total kinetic energy of the system before the collision is equal to the total kinetic energy after the collision. In an elastic collision, the objects involved bounce off each other without any loss of kinetic energy. This is in contrast to an inelastic collision, where some of the kinetic energy is lost and converted into other forms of energy such as heat or sound. A perfectly elastic collision is a special case of an elastic collision where there is no loss of kinetic energy at all. A perfectly inelastic collision, on the other hand, is a type of collision where the objects stick together and move as one after the collision, resulting in a loss of kinetic energy.

If a nonzero net force is acting on an object, it means that there is an unbalanced force acting on the object. According to Newton's second law of motion, an unbalanced force will cause an object to accelerate. Therefore, the correct answer is b. being accelerated.

Work is defined as the transfer of energy that occurs when a force is applied to an object and causes it to move in the direction of the force. In order for work to be done, there must be a displacement of the object caused by the force. Therefore, option c is the correct answer as it states that work is done whenever a force causes a displacement of the object. Options a, b, and d are not necessarily true as work can be done even if the force is not perpendicular to the displacement, or if there are multiple forces acting on the object.

The mechanical energy of a system of objects is the sum of kinetic energy and all relevant forms of potential energy. This means that it includes not only the energy associated with the motion of the objects (kinetic energy), but also the energy associated with their position or configuration (potential energy). This can include gravitational potential energy, elastic potential energy, and any other form of potential energy that is relevant to the system. By considering all forms of potential energy, the answer c encompasses a broader range of energy forms and provides a more comprehensive understanding of the mechanical energy of the system.

If Earth's distance from the sun increased by 4 times, the speed of Earth's orbit around the sun would decrease. This is because according to Kepler's laws of planetary motion, the speed of a planet in its orbit is inversely proportional to its distance from the sun. As the distance increases, the gravitational pull decreases, causing the planet to move slower. In this case, if the distance increases by a factor of 4, the speed would decrease by a factor of 2.

The region of a sound wave in which the density and pressure are greater than normal is called compression. Compression occurs when the particles in the medium are pushed closer together, resulting in an increase in density and pressure. This is in contrast to rarefaction, which is the region of a sound wave where the density and pressure are lower than normal. The amplitude of a sound wave refers to the maximum displacement of particles from their equilibrium position, while wavelength is the distance between two consecutive points in a wave.

When the two pulses overlap exactly, they will interfere with each other. If the first pulse is reflected back and meets the second pulse exactly, they will have opposite displacements at every point. This means that the positive displacement of one pulse will be canceled out by the negative displacement of the other pulse, resulting in a net displacement of zero. Therefore, the amplitude of the resultant pulse will be zero.

Magnetic field lines do form closed loops. They start from the north pole of a magnet, curve around the magnet, and end at the south pole. This is known as the magnetic field line pattern. Therefore, option b is not true.

The statement "The closer the force is to the axis of rotation, the less torque is produced" is correct because torque is the product of force and the perpendicular distance from the axis of rotation. When the force is closer to the axis of rotation, the perpendicular distance decreases, resulting in a smaller torque. This can be understood using the equation for torque, which is given by Torque = Force x Distance x sin(theta), where theta is the angle between the force vector and the direction of the lever arm. As the distance decreases, the torque decreases. Therefore, the statement is correct.

When the mass attached to a spring is at the equilibrium position, it has the maximum potential energy and the minimum kinetic energy. As the mass starts moving away from the equilibrium position, the potential energy decreases and the kinetic energy increases. This means that the velocity of the mass increases until it reaches a maximum when it is furthest from the equilibrium position. Therefore, option b is correct.

The components of a vector are perpendicular to each other. This means that they are at right angles to each other and do not depend on the orientation of the vector. The magnitude of the vector is not necessarily equal to half the magnitude of each component, and while vectors are indeed vector quantities, this is not the specific characteristic being described here. Therefore, the correct answer is c. perpendicular.

Using a machine allows you to use less force to do a given amount of work. Machines are designed to multiply or change the direction of the force applied, making it easier to perform tasks that would require more force if done manually. By using a machine, you can achieve the same amount of work with less effort, reducing the physical strain on the person performing the task.

When a car travels around a circular track at a constant speed, its velocity is zero because the car is constantly changing direction but not changing speed. Acceleration is also zero because acceleration is the rate of change of velocity, and since the car is not changing its speed or direction, there is no acceleration. Therefore, both acceleration and velocity are zero in this scenario.

In vector addition, the resultant vector is obtained by placing the tail of the second vector at the head of the first vector. Looking at diagram II, we can see that the tail of vector B is placed at the head of vector A, which is the correct representation of vector addition. Therefore, diagram II represents the vector addition C = A + B.

If the net force acting on an object is zero, it means that the object is in equilibrium. In this case, the object may have a non-zero velocity, but it does not have to be constant. The object could be moving at a constant velocity, but it could also be at rest or moving with a changing velocity. Therefore, statement b is false.