Physics C:

Magnetism

100

A bar magnet is falling through a wire loop and its north pole enters the loop first. As the magnet leaves the loop, the induced current as viewed from above is A. clockwise B. anticlockwise C. parallel to the magnet D. perpendicular to the magnet E. zero. F. none of the above.

What is B. anticlockwise?

200

A 2m long wire carrying a current of 12A to the north experiences a magnetic field of 3T into the page. What is the magnetic force on the wire? A. 72 N to the north B. 72 N to the south C. 72 N to the east D. 72 N to the west E. 0 N F. none of the above

What is D. 72N to the west

300

A uniform magnetic field B is directed into the page. An electron enters this field with initial velocity v to the right. Which of the following best describes the path of the electron while it is still within the magnetic field? A. It moves in a straight line. B. It bends upward in a parabolic path. C. It bends downward in a parabolic path. D. It bends upward in a circular path. E. It bends downward in a circular path. F. none of the above

What is E. It bends downward in a circular path?

400

What is the magnitude of the magnetic field produced at the center of a toroid with 50 loops, inner radius 4 cm, outer radius 6 cm, and a current of 2A clockwise? A. 0 T B. 5*10^-6 T C. 3.33*10^-6 T D. 1*10^-5 T E. none of the above

What is A. 0 T?

500

A wire loop is placed right above another wire loop. If the current flows in the upper loop anticlockwise and is increasing, the current in the lower loop will A. flow anticlockwise and be decreasing. B. flow anticlockwise and be increasing. C. flow clockwise and be increasing. D. flow clockwise and be decreasing. E. stay zero. F. none of the above

What is C. flow clockwise and be increasing?

Newton's Laws

100

A cannon is mounted on a truck that moves forward at a speed of 5 m/s. The operator wants to launch a ball from a cannon so the ball goes as far as possible before hitting the level surface. The muzzle velocity of the cannon is 50 m/s. What angle from the horizontal should the operator point the cannon? A. 5° B. 41° C. 45° D. 49° E. 85° F. none of the above

What is D. 49°?

200

A car moving with speed v reaches the foot of an incline of angle θ. The car coasts up the incline without using the engine. Neglecting friction and air resistance, which of the following is correct about the magnitude of the car's horizontal acceleration x and vertical acceleration y? A. x = 0; y < g B. x = 0; y = g C. x < g ; y < g D. x < g ; y = g E. x < g ; y > g F. none of the above

What is C. x < g ; y < g?

300

Which of the following conditions are necessary for an object to be in static equilibrium? (i) The vector sum of all torques on the object must equal zero. (ii) The vector sum of all forces on the object must equal zero. (iii) The sum of the object's potential and kinetic energies must be zero. A. I only B. II only C. III only D. I and II only E. I, II, and III F. none of the above

What is D. I and II only?

400

A sphere, a cube, and a cylinder, all of equal mass, are released from rest from the top of a short incline. The surface of the incline is extremely slick, so much so that the objects do not rotate when released, but rather slide with negligible friction. Which reaches the base of the incline first? A. the sphere B. the cube C. the cylinder D. All reach the base at the same time. E. The answer depends on the relative sizes of the objects.

What is D. All reach the base at the same time?

500

The Space Shuttle orbits 300 km above the Earth's surface; the Earth's radius is 6400 km. What is the acceleration due to Earth's gravity experienced by the Space Shuttle? A. 4.9 m/s2 B. 8.9 m/s2 C. 9.8 m/s2 D. 0.8 m/s2 E. zero

What is B. 8.9 m/s^2?

Electricity

100

A charged insulator and an uncharged conductor... A. always repel each other. B. always attract each other. C. exert no electrostatic force on each other. D. may attract or repel, depending on whether the charge is positive or negative. E. none of the above

What is B. always attract each other?

200

Experimenter A uses a very small test charge qo, and experimenter B uses a test charge 2qo to measure an electric field produced by two parallel plates. A finds a field that is A. greater than the field found by B B. the same as the field found by B C. less than the field found by B D. either greater or less than the field found by B, depending on the accelerations of the test charges E. either greater or less than the field found by B, depending on the masses of the test charges F. none of the above

What is B. the same as the field found by B?

300

A hollow metal ring of radius r carries charge q. Consider an axis straight through the center of the ring. At what point(s) along this axis is/are the electric field equal to zero? A. only at the center of the ring B. only at the center of the ring, and a very long distance away C. only a very long distance away D. only at the center of the ring, a distance r away from the center, and a very long distance away E. everywhere along this axis F. none of the above

What is B. only at the center of the ring, and a very long distance away?

400

Two identical capacitors are hooked in parallel to an external circuit. Which of the following quantities must be the same for both capacitors? (i) the charge stored on the capacitor (ii) the voltage across the capacitor (iii) the capacitance of the capacitor A. I only B. II only C. II and III only D. I and III only E. I, II, and III F. none of the above

What is E. I, II, and III?

500

A metal sphere carries charge Q; a nonconducting sphere of equal size carries the same charge Q, uniformly distributed throughout the sphere. These spheres are isolated from each other. Consider the electric field at the center of the spheres, within the spheres, and outside the spheres. Which of these electric fields will be the same for both spheres, and which will be different? (Center) (Elsewhere within sphere) (Outside sphere) A. same same same B. same same different C. same different same D. different different same E. different different different F. none of the above

What is C. same different same?

Rotational Motion

100

A force, F = (5x + 4y) N, is applied to an object at a point whose position vector with respect to the pivot point is r = (5x + 4y + 3z) m. Calculate the torque created by the force about that pivot point. A. 12x + 10y + 0z B. 12x + 15y + 0z C. 12x - 10y + 0z D. 12x - 15y + 0z E. zero E. none of the above

What is D. 12x - 15y + 0z?

200

A disk X rotates freely with angular velocity w on frictionless bearings. A second identical disk Y, initially not rotating, is placed on X so that both disks rotate together without slipping. When the disks are rotating together, which of the following is half what it was before? A. Moment of inertia of X B. Moment of inertia of Y C. Angular velocity of X D. Angular velocity of Y E. Angular momentum of both disks

What is C. Angular velocity of X?

300

A rigid rod of length L and mass M is floating at rest in space far from a gravitational field. A small blob of putty of mass m < M is moving to the right, towards the rpd. The putty hits and sticks to the rod a distance 2L/3 from the top end. What quantities are conserved in this collision? A. linear and angular momentum, but not kinetic energy B. linear momentum only C. angular momentum only D. linear and angular momentum, and linear but not rotational kinetic energy E. linear and angular momentum, and linear and rotational kinetic energy

What is A. linear and angular momentum, but not kinetic energy?

400

The 1.0-m-long non-uniform plank, shown above, has weight 1000 N. It is to be supported by two rods, A and B, as shown above. The center of mass of the plank is 30 cm from the right edge. Each support bears half the weight of the plank. If support B is 10 cm from the right-hand edge, how far from the left-hand edge should support A be? A. 0 cm B. 10 cm C. 30 cm D. 50 cm E. 70 cm

What is D. 50 cm?

500

A mass m is attached to a mass 3m by a rigid bar of negligible mass and length L. Initially, the smaller mass is located directly above the larger mass, as shown above. How much work is necessary to flip the rod 180° so that the larger mass is directly above the smaller mass? A. 4mgL B. 2mgL C. mgL D. 4 pi mgL E. 2 pi mgL F. none of the above

What is B. 2mgL?

Potpourri (real)

100

Two isolated particles, A and B, are 4 m apart. Particle A has a net charge of 2Q, and B has a net charge of Q. The ratio of the magnitude of the electric force on A to that on B is A. 4:1 B. 2:1 C. 1:1 D. 1:2 E. 1:4 F. none of the above

What is C. 1:1?

200

Free Response How many people were in Ms. Matney's 5th period class at the beginning of the school year?

What is 14 students?

300

A uniform magnetic field B points parallel to the ground. A toy car is sliding down a frictionless plane inclined at 30°. A loop of wire of resistance R and cross-sectional area A lies in the flat plane of the car's body. What is the magnetic flux through the wire loop? A. zero B. BA cos 30° C. BA cos 60° D. BA E. (BA cos 60°)/R F. none of the above

What is C. BA cos 60°?

400

True/False You can use your left hand to find the direction of magnetic force.

What is true?

500

The best teacher in the WOOOOOOOORRRRRLLLLLLLLD

Who is Ms. Matney?