1.
A boat travels 12.0 m while it reduces its velocity from 9.5 m/s to 5.5 m/s. What is the magnitude of the boat’s acceleration while it travels the 12.0 m?
Correct Answer
A. 2.5 m/s2
Explanation
The boat's acceleration can be calculated using the equation: acceleration = (final velocity - initial velocity) / time. In this case, the initial velocity is 9.5 m/s, the final velocity is 5.5 m/s, and the time is not given. However, since the boat travels a distance of 12.0 m, we can use the equation: distance = (initial velocity + final velocity) / 2 * time. Rearranging the equation to solve for time, we get: time = distance / ((initial velocity + final velocity) / 2). Plugging in the given values, we find that time = 12.0 m / ((9.5 m/s + 5.5 m/s) / 2) = 2.0 s. Plugging in the values for initial velocity, final velocity, and time into the acceleration equation, we find that acceleration = (5.5 m/s - 9.5 m/s) / 2.0 s = -4.0 m/s^2. However, since we are asked for the magnitude of the acceleration, the negative sign is ignored, giving us an answer of 4.0 m/s^2.
2.
A warehouse employee is pushing a 30.0 kg desk across a floor at a constant speed of 0.50 m/s. How much work must the employee do on the desk to change the speed to 1.00 m/s?
Correct Answer
A. 11.3 J
Explanation
The work done on an object can be calculated using the equation: work = force x distance. In this case, the force applied to the desk is equal to the force of friction, which is equal to the weight of the desk (mass x gravity). Since the speed is constant, the net force on the desk is zero, meaning that the force of friction and the force applied by the employee are equal in magnitude and opposite in direction. Therefore, the work done by the employee is equal to the force of friction multiplied by the distance the desk is pushed. As the speed doubles, the work done also doubles. Therefore, to change the speed from 0.50 m/s to 1.00 m/s, the employee must do twice the amount of work, which is 11.3 J.
3.
An object with an initial velocity of 3.50 m/s moves east along a straight and level path. The object then undergoes a constant acceleration of 1.80 m/s2 east for a period of 5.00 s. How far does the object move while it is accelerating?
Correct Answer
A. 40.0 m
Explanation
The object's initial velocity is given as 3.50 m/s and it undergoes a constant acceleration of 1.80 m/s^2 for a period of 5.00 s. To find the distance the object moves while accelerating, we can use the equation: distance = initial velocity * time + (1/2) * acceleration * time^2. Plugging in the values, we get: distance = 3.50 m/s * 5.00 s + (1/2) * 1.80 m/s^2 * (5.00 s)^2 = 17.5 m + 22.5 m = 40.0 m. Therefore, the object moves a distance of 40.0 m while it is accelerating.
4.
Which of the following best determines the amount of energy of a single photon of light?
Correct Answer
A. The frequency of the photon
Explanation
The amount of energy of a single photon of light is determined by its frequency. The frequency of a photon refers to the number of complete cycles it completes in a given unit of time. According to the equation E = hf, where E is the energy of the photon, h is Planck's constant, and f is the frequency of the photon, it can be observed that the energy of a photon is directly proportional to its frequency. Therefore, the frequency of the photon best determines its energy.
5.
A car traveling on a level road initially has 440 kJ of mechanical energy. After the brakes are applied for a few seconds, the car has only 110 kJ of mechanical energy. What best accounts for the missing mechanical energy?
Correct Answer
A. Most of the missing mechanical energy has been converted to heat energy through friction.
Explanation
When the brakes are applied, the car experiences friction between the brake pads and the wheels. This friction converts mechanical energy into heat energy, causing a loss in mechanical energy. Since the car loses a significant amount of mechanical energy (440 kJ to 110 kJ), it suggests that most of the missing mechanical energy has been converted to heat energy through friction.
6.
Which statement best explains the difference between light waves traveling through a vacuum and light waves traveling through a medium?
Correct Answer
A. Light waves traveling through a vacuum travel faster than light waves traveling through a medium.
Explanation
Light waves traveling through a vacuum travel faster than light waves traveling through a medium because a vacuum has no particles to interact with, while a medium, such as air or water, has particles that can slow down the speed of light.
7.
Which of the following is the best evidence that work has been done on or by an object?
Correct Answer
A. The energy of the object has changed.
Explanation
When work is done on or by an object, it results in a change in the object's energy. Work is defined as the transfer of energy from one object to another, or the transformation of energy from one form to another. Therefore, if the energy of the object has changed, it is the best evidence that work has been done on or by the object. The other options, such as the velocity of the object remaining constant, the mass of the object changing, or the direction the object is moving remaining constant, do not necessarily indicate the presence of work being done on or by the object.
8.
An engineer is designing an instrument to examine the interior of a piece of wood without cutting it. The engineer decides to pass electromagnetic radiation through the wood to a detector on the other side. Which type of electromagnetic radiation would be most suitable for this investigation?
Correct Answer
A. X-rays
Explanation
X-rays would be the most suitable type of electromagnetic radiation for this investigation because they have a shorter wavelength and higher energy compared to visible light, radio waves, and ultraviolet light. This allows X-rays to penetrate through materials, such as wood, without being absorbed or scattered significantly. By passing X-rays through the wood and detecting them on the other side, the engineer can obtain images or information about the interior structure of the wood without the need for cutting it.
9.
What is the impulse on a 45,000 kg airplane when it changes its velocity from 242 m/s to 258 m/s?
Correct Answer
A. 720,000 kg⋅m/s
Explanation
The impulse on an object can be calculated using the equation Impulse = Mass x Change in Velocity. In this case, the mass of the airplane is 45,000 kg and the change in velocity is 258 m/s - 242 m/s = 16 m/s. Therefore, the impulse on the airplane is 45,000 kg x 16 m/s = 720,000 kg⋅m/s.
10.
A train passes a stationary observer. Which of the following best describes how the amplitude and the apparent frequency of the sound waves heard by the observer change as the train moves away?
Correct Answer
A. Both the amplitude and the apparent frequency decrease.
Explanation
As the train moves away from the stationary observer, the sound waves it produces will experience the Doppler effect. The Doppler effect causes a decrease in both the amplitude and the apparent frequency of the sound waves. This means that the sound will become quieter (decrease in amplitude) and the pitch will appear lower (decrease in apparent frequency) to the observer. Therefore, the correct answer is that both the amplitude and the apparent frequency decrease.
11.
Which action will not induce a potential difference in a coil of wire?
Correct Answer
A. Holding the coil in a stationary magnetic field
Explanation
Holding the coil in a stationary magnetic field will not induce a potential difference in the coil of wire because there is no change in the magnetic field or the flux passing through the coil. According to Faraday's law of electromagnetic induction, a change in magnetic field or flux is required to induce a potential difference in a coil of wire. Therefore, holding the coil in a stationary magnetic field will not cause any change and hence, no potential difference will be induced.
12.
Which situation is a good example of the transfer of energy through radiation?
Correct Answer
A. A snake’s body temperature increases when the snake lies in the sun.
Explanation
When a snake lies in the sun, its body temperature increases. This is a good example of the transfer of energy through radiation because the snake absorbs the heat energy from the sun's rays. Radiation is the transfer of energy through electromagnetic waves, and in this case, the snake is absorbing the radiant heat energy from the sun.
13.
Two people each have a mass of 55 kg. They are both in an elevator that has a mass of 240 kg. When the elevator begins to move, the people and the elevator have an upward acceleration of 1.00 m/s2. What is the net force that acts on the elevator as it accelerates upward at 1.00 m/s2?
Correct Answer
A. 350 N
Explanation
The net force that acts on the elevator can be calculated using Newton's second law, which states that force is equal to mass multiplied by acceleration. In this case, the mass of the elevator and the people combined is 295 kg (240 kg + 55 kg + 55 kg) and the acceleration is 1.00 m/s^2. Therefore, the net force is equal to 295 kg * 1.00 m/s^2, which is equal to 295 N.
14.
The center of a 910 kg satellite is 9.9×106 m from Earth’s center. What is the gravitational force between the satellite and Earth?
Correct Answer
A. 3.7×103N
Explanation
The gravitational force between two objects can be calculated using the formula F = G * (m1 * m2) / r^2, where F is the gravitational force, G is the gravitational constant, m1 and m2 are the masses of the two objects, and r is the distance between their centers. In this case, the mass of the satellite is not given, but it is not needed to calculate the force. The distance between the centers of the satellite and Earth is given as 9.9×10^6 m. Plugging in the values into the formula, we can calculate the gravitational force to be 3.7×10^3 N.
15.
Two charged spheres are 16 cm apart. If the spheres are moved closer to each other so that they are 8 cm apart, how will the force between them change?
Correct Answer
A. The force will increase by a factor of 4.
Explanation
When the distance between the charged spheres is halved from 16 cm to 8 cm, the force between them will increase by a factor of 4. This is because the force between two charged objects is inversely proportional to the square of the distance between them. Therefore, when the distance is halved, the force will increase by a factor of (1/0.5)^2 = 4.
16.
A musical note has a frequency of 512 Hz. If the wavelength of the note is 0.685 m, what is the speed of the sound of that note?
Correct Answer
A. 351 m/s
Explanation
The speed of sound can be calculated using the formula speed = frequency * wavelength. In this case, the frequency is given as 512 Hz and the wavelength is given as 0.685 m. By multiplying these values together, we get a speed of 351 m/s.
17.
A bus is moving forward at 20 m/s. A student on the bus throws a tennis ball horizontally at 15 m/s toward the front of the bus. From the perspective of an observer on the sidewalk outside the bus, the tennis ball appears to move at —
Correct Answer
A. 35 m/s
Explanation
When the student throws the tennis ball horizontally towards the front of the bus, the ball already has the forward velocity of the bus, which is 20 m/s. Therefore, the total velocity of the ball from the perspective of an observer on the sidewalk is the sum of the ball's initial velocity (15 m/s) and the bus's velocity (20 m/s). This results in a total velocity of 35 m/s.
18.
Which action makes use of a magnetic force?
Correct Answer
A. A person puts a bank card in an electronic reader to buy an item.
Explanation
When a person puts a bank card in an electronic reader, the magnetic strip on the card is read by the reader using a magnetic force. This magnetic force allows the reader to retrieve the information stored on the card, such as the person's account number and transaction details.
19.
Sound travels through air at a speed of 342 m/s at room temperature. What is the frequency of a sound wave with a wavelength of 1.8 m, to the nearest whole Hz?
Correct Answer
A. 190
Explanation
The frequency of a sound wave can be calculated using the formula: frequency = speed of sound / wavelength. In this case, the speed of sound is given as 342 m/s and the wavelength is given as 1.8 m. By dividing the speed of sound by the wavelength, we can find the frequency of the sound wave. Therefore, the frequency is approximately 190 Hz.
20.
Suppose Earth orbited a star whose mass was double the mass of the sun. If the radius of Earth’s orbit remained the same as it is now, then compared with the gravitational force between Earth and the sun, the gravitational force between Earth and the star would be —
Correct Answer
A. Two times as much
Explanation
If the mass of the star is double that of the sun and the radius of Earth's orbit remains the same, then according to Newton's law of universal gravitation, the gravitational force between Earth and the star would be directly proportional to the mass of the star. Therefore, if the mass of the star is double that of the sun, the gravitational force between Earth and the star would also be double the gravitational force between Earth and the sun. Hence, the gravitational force between Earth and the star would be two times as much.