Physics - Mich Trial

Question 1

4.11 Write down the relationship between work done, force and distance moved in the direction of the force

Answer 1

Work Done = Force x Distance (parallel to the force)

W = F x D

Question 2

4.12 How is work done and energy transferred related?

Answer 2

Work Done = Energy Transferred

Question 3

4.13 Write down the relationship between gravitational potential energy, mass, gravitational field strength and height

Answer 3

Gravitational Potential Energy = Mass x Gravitational Field Strength x height

GPE = mgh

Question 4

4.14 Write down the relationship between kinetic energy, mass and speed

Answer 4

Kinetic Energy = 0.5 x mass x speed squared

KE = 1/2mv^2

Question 5

4.15 Write down the relationship between gravitational potential energy and kinetic energy of an object when it is dropped or thrown in the air

Answer 5

Change in KE = Change in GPE

Question 6

4.16 Define power

Answer 6

Rate of the transfer of energy or rate of doing work

Question 7

4.17 Write down the relationship between power, work done (energy transferred) and time taken

Answer 7

Power = Work Done/Time

P = W/t

Question 8

What is the unit for: Momentum

Answer 8

Kilogram metre/second

kg m/s

Question 9

What is the unit for: Moments

Answer 9

Newton Metre

Nm

Question 10

1.30P Write down the relationship between the moment of a force, force and perpendicular distance from a pivot in words and symbols

Answer 10

Turning moment of a force = force x perpendicular distance to the pivot

M = F x D

Question 11

1.31P State where the weight of an object, such as a rod, can be considered to act from

Answer 11

The centre of gravity of the object

Question 12

1.32P State the principle of moments

Answer 12

In equilibrium, the sum of the clockwise moments = sum of the anticlockwise moments

Question 13

1.32P Describe how to use the principle of moments with several parallel forces acting on an object

Answer 13

All forces are balanced - so the clockwise forces and anticlockwise forces will be the same.

Also the vertical and horizontal forces are balanced so force to the left = force to the right, upwards force = downwards force

Question 14

1.33P Describe how the upwards force generated by two pivots supporting a beam is affected by the position of a heavy object placed on the beam

Answer 14

The pivot closest to the mass provides the greatest force

As the mass moves towards the other mass, the other mass provides a greater force and the original mass provided less force.

Question 15

7.17 State the nuclear processes that can be a source of energy

Answer 15

Fission, Fusion, and radioactive decays

Question 16

7.18 Describe fission of U-235

Answer 16

U-235 can be split (the process of fission) by collision with a neutron, and this produces two smaller daughter nuclei of roughly equal size and a small number of neutrons

Question 17

7.18 How is the energy released in a fission process

Answer 17

Kinetic Energy of the fission products

Question 18

7.19 State what is produced from the fission of U-235

Answer 18

A small number of neutrons and two daughter nuclei

Question 19

7.20 describe how a chain reaction can be set up

Answer 19

The neutrons produced by one fission strike other U-235 nuclei causing it to undergo another fission reaction.

This happens repeatedly.

Question 20

7.21 Describe the role played by the control rods in the fission process

Answer 20

The boron control rods absorb excess neutrons to slow down the reactions so it will be stable

Question 21

7.12 Describe the role played by the moderator in the fission process

Answer 21

The moderator - made of graphite or water - slows down the neutrons so that they are more likely to be absorbed by U-235

Question 22

7.22 Describe the role of shielding around a nuclear reactor and what it is made from

Answer 22

Shielding absorbs the high energy gamma rays and neutrons produced in fission.

It is made from thick concrete or lead.

Question 23

7.23 Explain the difference between nuclear fusion and nuclear fission

Answer 23

Fission is the splitting of a large nucleus into two smaller nuclei and a small number of neutrons.

Fusion is the combining of two small nuclei into a larger nucleus.

Question 24

6.11P Describe the force on a charged particle in a magnetic field

Answer 24

When there is a charged particle moving through a magnetic field, there is a force - provided it is not moving parallel to the magnetic field.

The force is perpendicular to the direction of motion and the direction of the magnetic field.

Left hand rule:
First finger - Magnetic Field
Second finger - Current
Thumb - Force

Question 25

6.12 Explain why a force is exerted on a current-carrying wire in a magnetic field

Answer 25

The magnetic field of the wire interacts with the external magnetic field creating a force

Question 26

6.12 Describe how a d.c. electric motor works

Answer 26

SEE ONENOTE FOR DIAGRAM

A current is passed through the coil.
This creates a magnetic field which interacts with that of the permanent magnet - a force is created.
The split ring commutator changes the direction of the current around the loop every half turn.
Therefore the interaction produces a force that is always in the same direction of motion - so the coil keeps spinning in that motion

Question 27

6.12 Describe how a loudspeaker works

Answer 27

A coil is placed on a permanent magnet
An a.c. signal is passed through the coil which is wrapped around the base of a cone.
An alternating force is created between the two magnetic fields
This causes the coil to move backwards and forwards.
This causes the cone to vibrate and make sound.

Question 28

6.13 A wire carries a current perpendicular to a magnetic field. Describe how to determine the direction of the force on the wire.

Answer 28

Use the left-hand rule

First finger – magnetic field (finger points from north to south)

Second finger – current (direction of conventional current and the direction a positive charge is moving)

Thumb – motion/thrust (the direction of the force)

Question 29

6.14 Describe factors that increase the force on a current-carrying conductor in a magnetic field, such as the coil in a motor or speaker

Answer 29

More current
More turns on the coil
Stronger magnetic field
Soft iron core in the coil

Question 30

6.14 Describe how the direction of the force on a current-carrying conductor in a magnetic field can be changed

Answer 30

Change the direction of the current or the poles of the magnet