2013. Category 2: Forces

The ammeter above shows the current produced by a series of solar cell that contain zinc plates being used to power a single series circuit.

If the circuit's resistance is 0.2 Ω, what voltage is supplied by the cells?

• 750 V

• 15 V

• 3 V

• 25 V

The center of a 910 kg satellite is 9.9 x 10^{6 m} from Earth's center. What is the gravitational force between the satellite and Earth?

• 4.5 x 10³ N

• 3.7 x 10³ N

• 8.9 x 10³ N

• 1.7 x 10⁶ N

Before 1820 magnetism and electricity were believed to be different types of forces caused by different physical processes. In 1820 Hans Christian Orsted conducted an experiment with compasses and wire. The diagram above shows the results of his experiment. This experiment was important because it -

• showed how to make a compass point in a direction other than north

• was the first to show electric current flowing in a straight line

• showed that electricity and magnetism are related

• proved that magnetism is an extremely weak force compared with electricity

Two charged spheres are 16 cm apart. If the spheres are moved closer to each other so that they are 8 c apart, how will the force between them change?

• The force will decrease by a factor of 2.

• The force will increase by a factor of 2.

• The force will decrease by a factor of 4.

• The force will increase by a factor of 4.

A schematic diagram of a circuit of two resistors is shown above.

What is the total resistance of the circuit?

• 12 Ω

• 3 Ω

• 2 Ω

• 0.33 Ω

Which action makes use of a magnetic force?

• A person puts a bank card in an electronic reader to buy an item.

• A store clerk finds the price of an item by moving the item over a laser light.

• A parent measures a child's temperature by touching a thermometer to the child's head.

• A student measures the mass of a book using a spring scale.

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 -

• half as much

• the same

• two times as much

• four times as much

The nucleus of a helium atom is an alpha particle, which consists of two protons and two neutrons.

Which statement best explains how the two protons in an alpha particle can be bound so closely together?

• The strong nuclear force and the electromagnetic force are the same.

• The strong nuclear force is weaker than the electromagnetic force.

• The strong nuclear force is stronger than the electromagnetic force.

• The strong nuclear force and the electromagnetic force are negligible.

A student makes a graph that shows the electric current through a resistor over time.

Which of the following conclusions does the graph best support?

• The voltage across the resistor decrease until it becomes zero.

• The voltage across the resistor increases until it reaches a constant value.

• A fuse in the circuit blows after approximately 30 seconds.

• The resistance decreases as the voltage increases.

The table above shows some data for the moon.

Based on the table, what is the gravitational force on a 1.00 kg rock on the surface of the moon?

• 4.91 x 10¹² N

• 1.62 N

• 9.81 N

• 1.28 x 10²⁹ N