Midterm

1.

A concave mirror with a radius of 20 cm creates a real image 30 cm from the mirror. What is the object distance?

[removed]A) 5.0 cm [removed]B) 15 cm [removed]C) 20 cm [removed]D) 7.5 cm

2.

Starting from rest, a proton falls through a potential difference of 1200 V. What speed does it acquire?

[removed]A) 1.2 × m/s [removed]B) 2.4 × m/s [removed]C) 3.6 × m/s [removed]D) 4.8 × m/s

3.

An oil layer that is 5.0 cm thick is spread smoothly and evenly over the surface of water on a windless day. What is the angle of refraction in the water for a ray of light that has an angle of incidence of 45° as it enters the oil from the air above? (The index of refraction for oil is 1.15, and for water it is 1.33.)

[removed]A) 32° [removed]B) 27° [removed]C) 39° [removed]D) 36°

4.

Which of the equations here is valid for the circuit shown?

[removed]A) [removed]B) [removed]C) [removed]D) [removed]E)

5.

What current is flowing if 4.0 × electrons     pass a point in 0.50 s?

[removed]A) 6.3 A [removed]B) 78 A [removed]C) 0.31 A [removed]D) 0.013 A

6.

Two charges are separated by a distance d and exert mutual attractive forces of F on each other. If the charges are separated by a distance of d/3, what are the new mutual forces? D) 9F

[removed]A) 3F [removed]B) 9F [removed]C) F/3 [removed]D) F/9

7.

A point charge of +Q is placed at the centroid of an equilateral triangle. When a second charge of +Q is placed at one of the triangle’s vertices, an electrostatic force of 4.0 N acts on it. What is the magnitude of the force that acts on the center charge due to a third charge of +Q placed at one of the other vertices?

[removed]A) zero [removed]B) 8.0 N [removed]C) 16 N [removed]D) 4.0 N

8.

Two long parallel wires carry currents of 20 A and 5.0 A in opposite directions. The wires are separated by 0.20 m. At what point between the two wires are the contributions from the two wires the same?

[removed]A) 0.080 m from the 20 A wire [removed]B) 0.16 m from the 20 A wire [removed]C) 0.040 m from the 20 A wire [removed]D) 0.12 m from the 20 A wire

9.

Estimate the average power output of the Sun, given that about 1350 W/  reaches the upper atmosphere of the Earth. The distance from the Sun to the Earth is 1.5 ×  m.

[removed]A) 1 × W [removed]B) 3 ×   W [removed]C) 4 ×   W [removed]D) 2 ×  W

10.

A flux of 4.0 ×  Wb is maintained through a coil for 0.50 s. What emf is induced in this coil by this flux?

[removed]A) [removed]B) [removed]C) No emf is induced in this coil. [removed]D)