Physics Final Exam
A 200-N sled slides down a frictionless hillside that rises at 37 above the horizontal. What is the magnitude of the force that the hill exerts on the sled parallel to the surface of the hill?
0 N
As shown in the figure, a given force is applied to a rod in several different ways. In which case is the torque about the pivot P due to this force the greatest?
1
A force produces power P by doing work W in a time T. What power will be produces by a force that does six times as much work in half as much time?
12P
A 200-N sled slides down a frictionless hillside that rises at 37 above the horizontal. What is the magnitude of the force that the surface of the hill exerts on the sled?
160 N
When you drop a pebbles from height H, it reaches the ground with kinetic energy K if there is no air resistance. From what height should you drop it so it will reach the ground with twice as much kinetic energy
2H
Two small objects, with masses m and M, are originally a distance r apart, and the magnitude of the gravitational force on each one is F. The second object had its mass changed to 2M, and distance is changed to r/4. What is the magnitude of the new gravitational force?
32F
Four point charges of equal magnitude but with varying signs are arranged on three of the corners and at the center of the square of side d as shown in the figure. Which one of the arrows shown represents the net force acting on the center charge?
A
Four point charges of varying magnitude and sign are arranged on the corners of the square of side d as shown in the figure. Which one of the arrows shown represents the net force acting on the point charge with charge +Q?
A
Three equal-magnitude point charges of varying signs are placed at three of the corners of a square of side d as shown in the figure. Which one of the arrows shown represents the direction of the net electric field at the center of the square?
A
Which one of the arrows shown in the figure best represents the direction of the electric field between the two uniformly charged metal plates?
A
The figure shows scale drawings of four objects, each of the same mass and uniform thickness, with the mass distributed uniformly. Which one has the greatest moment of inertia when rotated about an axis perpendicular to the plane of the drawing at point P?
B
Three equal negative point charges -q are placed at three of the corners of a square of side d as shown in the figure. Which one of the arrows shown represents the direction of the net electric field at the vacant corner of the square?
B
Two blocks, A and B, are being pulled to the right along a horizontal surface by a horizontal 100-N pull, as shown in the figure. Both of them are moving together at a constant velocity of 2.0 m/s to the right, and both weigh the same. Which of the figures below shows a correct free-body diagram of the horizontal forces acting on the lower block, B?
B (100 N in both directions)
Two objects of unequal masses, M and m (M > m), are connected by a very light cord passing over an ideal pulley of negligible mass. When released, the system accelerates, and friction is negligible. Which one of the following free-body diagrams most realistically represents the forces acting on the two objects in the moving system?
C
Two blocks, A and B, are being pulled to the right along a horizontal surface by a horizontal 100-N pull, as shown in the figure. Both of them are moving together at a constant velocity of 2.0 m/s to the right, and both weigh the same. Which of the figures below shows a correct free-body diagram of the horizontal forces acting on the upper block, A?
E (no horizontal forces act on A.)
Two small balls, A and B, attract each other gravitationally with a force of magnitude F. If we now double both masses and the separation of the balls, what will now be the magnitude of the attractive force on each one?
F
Two small objects, with masses m and M, are originally a distance r apart, and the magnitude of the gravitational force on each one is F. The masses are changed to 2m and 2M, and the distance is changed to 4r. What is the magnitude of the new gravitational force?
F/4
A spinning ice skater on extremely smooth ice is able to control the rate at which she rotates by pulling in her arms. Which of the following statements are true about the skater during this process?
Her angular momentum remains constant
Two point charges, Q1 and Q2, are separated by a distance R. If the magnitudes of both charges are doubled and their separation is also doubled, what happens to the electrical force that each charge exerts on the other one?
It remains the same
Two wires are made out of the same metal. but one wire is twice as long as the other wire. Which wire will have the greatest elastic modulus?
It will be the same for both wires
When is the angular momentum of a system constant?
Only when no net external torque acts on the system.
Which one of the following is an accurate statement?
The ratio of tensile stress to tensile strain is called Young's Modulus
A negatively-charged rod is brought close to (but does not touch) two neutral spheres that are in contact with each other but insulated from the ground. If the two spheres are then separated, what kind of charge will be on the spheres?
The sphere near the charged rod becomes positive and the other one becomes negative
A 25-kg piece of equipment can be hung by steel wires of length 1.00m, 2.00m, and 3.00m. If all the wires have the same diameter, which one will stretch the greatest percent?
They will all stretch by the same percent
X and Y are two initially uncharged metal spheres on insulating stands, and they are in contact with each other. A positively charged rod R is brought close to X as shown in part (a) of the figure. Sphere Y is now moved away from X, as shown in part (b). What are the final charge states of X and Y?
X is negative and Y is positive
The graph in the figure shows the tensile stress as a function of the tensile strain in a certain wire. What does the slope of this graph give us for this wire?
Young's modulus for the material of the wire
A large 75-kg lightning fixture can be hung from wires of identical size and shape made of aluminum, brass, or copper. The values of Young's modulus for these metals are 0.70x10^11(aluminum), 0.91x10^11(brass), and 1.1x10^11(copper). Which wire would stretch the least distance?
aluminum
Tensile stress is
applied force per cross-sectional area
When an object moves in uniform circular motion, the direction of its acceleration is
directed toward the center of its circular path
The electric field at point P due to a point charge Q a distance R away from P has magnitude E. In order to double the magnitude of the field at P, you could
double the charge to 2Q
You are making a circular turn in your car on a horizontal road when you hit a big patch of ice, causing the force of friction between the tires and the road to become zero. While the car is on the ice, it
moves along a straight line path in its original direction
The figure shows electric field lines arising from two small charged particles P and Q. Consider the following two statements: (i) The charge on P is smaller than the charge on Q. (ii) The electrostatic force on P is smaller than the force on Q. Which of the above statements are true?
only (i) is true
A car goes around a circular curve on a horizontal road at constant speed. What is the direction of the friction force on the car due to the road?
perpendicular to the car inward
Two stationary point charges q1 and q2 are shown in the figure along with a sketch of some field lines representing the electric field produced by them. What can you deduce from the sketch?
q1 is negative and q2 is positive; the magnitude of q1 is less than the magnitude of q2
Tensile strain is
ratio of change in length to original length
A 25-kg piece of equipment can be hung by steel wires of length 1.00m, 2.00m, or 3.00m. If all the wires have the same diameter, which one will stretch the greatest distance?
the 3.00m wire
The reason an astronaut in an earth satellite feels weightless is that
the astronaut is falling
Two equal-magnitude forces are applied to a door at the doorknob. The first force is applied perpendicular to the door, and the second force is applied at 30° to the plane of the door. Which force exerts the greater torque about the door hinge?
the first force (applied perpendicular to the door)
Two forces produce equal torques on a door about the door hinge. The first force is applied at the midpoint of the door; the second force is applied at the doorknob. Both forces are applied perpendicular to the door. Which force has a greater magnitude?
the first force (at the midpoint)
An electron is initially moving to the right when it enters a uniform electric field directed upwards, as shown in the figure. Which trajectory (X, Y, Z, or W) will the electron follow in the field.
trajectory Z