U6 Revision - Further Mechanics, Fields and Particles

The table shows the charges on up quarks and down quarks.

Which row of the table shows the quark structure of protons and neutrons?

• A

• B

• C

• D

Answer explanation

C is the only correct answer here.

A, B & D are wrong because the charges on the quark combinations in those rows do not add up to 'e' and zero.

A laboratory centrifuge rotates at 1500 revolutions per minute.

Which of the following expressions gives the angular velocity in radians per second?

• 95 protons and 235 neutrons

• 93 protons and 144 neutrons

• 93 protons and 237 neutrons

• 89 protons and 138 neutrons

Answer explanation

Only B is correct here.

Nucleus X that emits the alpha particle will have 237 and 93 as its nucleon and proton numbers.

Therefore, it has 93 protons and 144 neutrons.

Which of the following statements is not a valid conclusion from alpha particle scattering experiments?

• Most of the atom is empty space.

• Most of the mass of the atom is concentrated in the nucleus.

• The nucleus contains all of the charge of the atom.

• The radius of the nucleus is very small compared to the radius of the atom.

Point charges of equal magnitude are placed close together, as shown.

Which of the following diagrams shows the electric field around the charges?

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Which of the following statements is true for a cyclotron?

• A cyclotron can be used to accelerate neutrons.

• A cyclotron uses a magnetic field to increase the speed of particles.

• A cyclotron uses an alternating potential difference at a constant frequency.

• A cyclotron uses an electric field to keep particles moving in a circular path.

A non-relativistic particle of mass m has momentum p and kinetic energy E_K .

A second non-relativistic particle of mass m/2 has momentum 2p.

Which of the following expressions gives the kinetic energy of the second particle?

• E_K / 2

• E_K

• 2E_K

• 8E_K

Answer explanation

D is the only correct answer here.

With the mass halving, the velocity will need to quadruple to give the new momentum of 2p. So the overall effect on the kinetic energy of halving the mass and quadrupling the velocity is to scale the kinetic energy up by a factor of 8.

A ball travelling at speed u towards a wall collides with the wall at right angles. The ball bounces off the wall at speed v in the opposite direction. The time for the collision is t. Which of the following expressions gives the average force on the wall during the collision?

• 4t

• 2t

• t/2

• t/4

The diagram shows equipotential lines about a point charge.

Which of the following diagrams shows a possible combination of electric field lines and polarity of point charge to produce this pattern?

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