1. Review the graph below. Which statement correctly describes what is happening to the object?
A. The object has constant velocity.
B. The object has constant acceleration.
C. The object is at rest. It is not moving.
D. The object has increasing acceleration.
E. The object has increasing inertia.
2. Which of the following creates a magnetic field?
A. the spinning and rotating of electrons in atoms
B. the separation of charged particles in atoms
C. the vibrational and translational motion of atoms
D. loosely held valence electrons surrounding an atom
E. a neutron:proton ratio greater than one
3. Which of the following creates an electromagnet?
A. rapidly spinning and rotating electrons inside an iron bar
B. an iron bar moving inside a coil of wire that contains a current
C. the movement of electrons through a complete circuit
D. convection currents within the liquid core of Earth’s interior
E. translational and vibrational motion of atoms
4. What is the definition of work?
A. the amount of energy used to accomplish a job
B. the force used to move a mass over a distance
C. the amount of power per unit of time
D. energy stored in an object due to its position
E. force multiplied by the time over which the force acts
5. How many calories of heat are absorbed by 100g of water as it heats up from 50ºC to 55ºC?
A. 5 calories
B. 50 calories
C. 500 calories
D. 550 calories
E. 5000 calories
6. What property of light explains why a pencil in a glass of water appears to be bent?
C. angle of incidence = angle of reflection
D. constructive interference
E. destructive interference
7. Which of the following statements is explained by quantum physics?
A. Light exhibits properties that are both wavelike and particle-like.
B. Matter and energy cannot be created or destroyed, only transformed.
C. All energy transformations result in a more disordered state.
D. Temperature can be thought of as the average kinetic energy of molecules.
E. The actual mechanical advantage of a machine cannot exceed 100 percent.
8. The force of gravity on Earth’s moon is 1/6 the force of gravity on the Earth. The force due to gravity on Earth is 9.81 m/s2. What is the weight of a 5 kg mass on the moon?
A. 0.833 N
B. 8.175 N
C. 30.00 N
D. 49.05 N
E. 294.30 N
9. 10 N of force are exerted on a sphere at an angle of 30º. An additional 10 N of force are exerted at an angle of 210º. Which statement about the sphere is correct?
A. The sphere is in a state of equilibrium and not moving.
B. The sphere is in a state of accelerating velocity.
C. The sphere is moving along a line at a 120º angle.
D. The sphere is experiencing additional g-force.
E. The sphere is moving in a circular path with a radius of 10N.
ANSWER KEY EXAM 237
1. Answer: B
The line on the velocity time graph represents acceleration. The slope indicates a constant rate of acceleration. The test taker who does not recognize the units on the y-axis (m/s) as velocity may incorrectly choose option a. The test taker who equates an upward slope with an increasing value may be drawn to option d. The test taker who does not understand inertia may be drawn to option E.
2. Answer: A
A magnetic field is created by a spin magnetic dipole moment and the orbital magnetic dipole moment of the electrons in atoms. Therefore, it is the spinning and rotating of electrons in atoms that creates a magnetic field. Choice b describes the nucleus and electron clouds within an atom. Choice c creates thermal energy. Choice d creates a good electrical conductor. Choice e creates a radioactive atom.
3. Answer: B
An iron bar moving inside a coil of wire that contains a current would create an electromagnet. Choice a creates a magnetic field. Choice c creates an electric current. Choice d creates the Earth’s magnetic field. Choice e creates thermal energy.
4. Answer: B
Work is defined as the force used to move a mass over a distance. Choice a may be a secular (non-scientific) definition of work. Choice c is the definition of power. Choice d is the definition of potential energy. Choice e is the definition of impulse.
5. Answer: C
One calorie is the amount of heat energy required to increase the temperature of 1 gram of water by 1 degree C. The test taker needs to know that the specific heat of water is 1 cal/g ºC. The correct calculation to solve this problem is:
(amount of water) x (specific heat of water) x (temperature change of water)
(100 g) x (1 cal / g ºC) x (55ºC – 50ºC) = 500 calories
6. Answer: B
Light travels in straight lines. As light moves from one substance to another, the light rays bend according to the refractive index of each substance. As the light travels through the air, it hits the non-submerged portion of the pencil. The light is reflected from the pencil and this is what we see. However, as the light travels into the water, the light waves are bent (refracted), and that light is subsequently reflected and travels to our eyes. What we perceive is a pencil that is no longer whole and straight, but broken and bent. It is refraction (choice b) that causes this perception.
Although the other distractors are also properties of waves, they are not the reasons why the observer perceives the pencil as bent.
7. Answer: A
A fundamental concept of quantum physics is wave-particle duality. The remaining choices, while fundamental concepts in physics, can be explained by Newtonian physics. Choice b is the Law of Conservation of Matter and Energy. Distractor c is the 2nd Law of Thermodynamics. Choice d is the Kinetic Molecular Theory. Choice e is an application of the 2nd Law of Thermodynamics.
8. Answer: B
Weight is the force of gravity acting on a mass. The combination of Newton’s 1st and 2nd Laws of Motion yields the mathematical formula F = ma. Applied to weight, this relationship can also be expressed as F = mg. To arrive at the correct answer, first multiply Earth’s gravity by 1/6 to calculate the gravity on the moon (g = 9.81 m/s2 x 1/6 = 1.635 m/s2). The second step is to multiply this value by the mass of the object (F = 5 kg x 1.635m/s2; F=8.175N).
The test taker who chooses a multiplied the mass by 1/6 and ignored the gravity component altogether. The test taker who chooses c divided the mass by 1/6 and ignored the gravity component altogether. The test taker who chooses d calculated the mass of the object on Earth and ignored the variable of the moon. The test taker who chooses e multiplied Earth’s gravity by 6 instead of dividing it by 6.
9. Answer: A
The two forces described in the item stem are equal in magnitude and opposite in direction. This creates a state of equilibrium and the sphere is not moving.
The conditions necessary for the sphere to accelerate (b) are a change in direction or a change in velocity. The equal and opposite forces described in the item stem will not create either condition.
The conditions necessary for the sphere to move along a line at a 120º angle (c) are two unequal forces acting at 30º and 210º.
G-force is a measure of acceleration. The conditions necessary for the sphere to experience additional g-force (d) are freefall or increasing acceleration. The equal and opposite forces described in the item stem will not create either condition.
A centripetal force on the sphere is required for the sphere to move in a circular path. 10N is a unit of force, not a unit of distance. Choice e is therefore incorrect.