Physics - Mich Trial Flashcards
4.11 Write down the relationship between work done, force and distance moved in the direction of the force
Work Done = Force x Distance (parallel to the force)
W = F x D
4.12 How is work done and energy transferred related?
Work Done = Energy Transferred
4.13 Write down the relationship between gravitational potential energy, mass, gravitational field strength and height
Gravitational Potential Energy = Mass x Gravitational Field Strength x height
GPE = mgh
4.14 Write down the relationship between kinetic energy, mass and speed
Kinetic Energy = 0.5 x mass x speed squared
KE = 1/2mv^2
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
Change in KE = Change in GPE
4.16 Define power
Rate of the transfer of energy or rate of doing work
4.17 Write down the relationship between power, work done (energy transferred) and time taken
Power = Work Done/Time
P = W/t
What is the unit for: Momentum
Kilogram metre/second
kg m/s
What is the unit for: Moments
Newton Metre
Nm
1.30P Write down the relationship between the moment of a force, force and perpendicular distance from a pivot in words and symbols
Turning moment of a force = force x perpendicular distance to the pivot
M = F x D
1.31P State where the weight of an object, such as a rod, can be considered to act from
The centre of gravity of the object
1.32P State the principle of moments
In equilibrium, the sum of the clockwise moments = sum of the anticlockwise moments
1.32P Describe how to use the principle of moments with several parallel forces acting on an object
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
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
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.
7.17 State the nuclear processes that can be a source of energy
Fission, Fusion, and radioactive decays
7.18 Describe fission of U-235
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
7.18 How is the energy released in a fission process
Kinetic Energy of the fission products
7.19 State what is produced from the fission of U-235
A small number of neutrons and two daughter nuclei
7.20 describe how a chain reaction can be set up
The neutrons produced by one fission strike other U-235 nuclei causing it to undergo another fission reaction.
This happens repeatedly.
7.21 Describe the role played by the control rods in the fission process
The boron control rods absorb excess neutrons to slow down the reactions so it will be stable
7.12 Describe the role played by the moderator in the fission process
The moderator - made of graphite or water - slows down the neutrons so that they are more likely to be absorbed by U-235
7.22 Describe the role of shielding around a nuclear reactor and what it is made from
Shielding absorbs the high energy gamma rays and neutrons produced in fission.
It is made from thick concrete or lead.
7.23 Explain the difference between nuclear fusion and nuclear fission
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.
6.11P Describe the force on a charged particle in a magnetic field
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
6.12 Explain why a force is exerted on a current-carrying wire in a magnetic field
The magnetic field of the wire interacts with the external magnetic field creating a force
6.12 Describe how a d.c. electric motor works
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
6.12 Describe how a loudspeaker works
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.
6.13 A wire carries a current perpendicular to a magnetic field. Describe how to determine the direction of the force on the wire.
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)
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
More current
More turns on the coil
Stronger magnetic field
Soft iron core in the coil
6.14 Describe how the direction of the force on a current-carrying conductor in a magnetic field can be changed
Change the direction of the current or the poles of the magnet
