Paper 2 Exam Questions

Question 1

Discuss the energy changes when an ion passes through an accelerator in a mass spec. Assume ions are in a perfect vacuum

(3 marks)

Answer 1

Potential energy of ion is transferred to kinetic energy of ion

Power supply transfers energy to the ion

Decrease in energy stored in supply = increase in kinetic energy stored by the ion

Question 2

Discuss how the path of an ion in the mass separator (whereby a magnetic field and electric field are perpendicular to each other) is affected when it has more nucleons

(2 marks)

Answer 2

R increases/ less curvature

Magnetic force is the same but m is directly proportional to m so r increases

r = mv
—-
Bq

Question 3

Compare, with justification, the path of a doubly charged ion through the mass spectrometer with that of a singly charged ion of the same mass

(3 marks)

Answer 3

Same path
Since Bqv = Eq so v is independent of q

Radius is decreased 
Since r = mv
               -----
                Bq
Where r is directly proportional to 1/q

Question 4

Impulse engines are used to place the satellite into an orbit with a longer period

Discuss any changes this makes to the orbital motion of the satellite

(4 marks)

Answer 4

Radius must increase

Velocity gets smaller

R^3 is directly proportional to T^2

(From circular motion) v^2 is directly proportional to 1/r

Question 5

Explain why, for a fixed volume, the pressure falls when gas is removed from the container

(4 marks)

Answer 5

1. Pressure is due to collisions between molecules
2. pV=1/3Nmc^2 where V, m and c^2 are constant
3. p is directly proportional to N
4. so if gas is removed, the number of molecules decreases so the number of collisions decreases

Question 6

Describe how the motion of gas molecules can be used to explain the pressure exerted by a gas on the walls of its container

(4 marks)

Answer 6

1. The molecules collide with the walls of the container
2. The wall exerts a force on the molecules causing its momentum to change
3. Molecule exerts equal but opposite force on the wall
4. Creating pressure

Question 7

Explain why the magnitude of emf is greatest at 90 and 270 degrees (3 marks) [5 possible points]

Answer 7

Induced emf is directly proportional to the rate of change of flux linkage
-flux linkage through the coil changes as it is rotated
From its maximum at 0 and 180 to zero at 90 and 270
Rate of change is greatest when plane of coil is parallel
Because coil then cuts flux lines perpendicularly

Question 8

Use the binding energy graph to explain how energy is released when some nuclides undergo fission and when other nuclides undergo fusion

(3 marks) 4 possible points

Answer 8

Energy is released when binding energy PER NUCLEON is increased
In fission a large nucleus splits and in fusion nuclei join
The most stable nuclei are at a peak
Fusion occurs to the left of the peak and fission occurs to the right

Question 9

Explain why nuclei in a star have to be at a high temperature for fusion to take place

(3 marks)

Answer 9

Nuclei must be close together for the strong nuclear force to be involved and so fusion can take place

But the electrostatic force is repulsive

High temp = high kinetic energy and speed to overcome repulsion

Question 10

Describe and explain the nature of the radiation emitted from a nucleus of the moderator after collision with a neutron

(2 marks)

Answer 10

Emits electromagnetic radiation

As the nucleus de-excites to a lower energy level