Physics End Of Year Exam Flashcards
The mean power output of the wind farm is 696 MW, which is enough power for 580 000 homes.
Calculate the mean power needed for 1 home.
1200 W
On one day the demand for electricity in the UK was 34000 MW
Suggest two reasons why wind power was not able to meet this demand
Wind is unreliable
Wind turbines don’t turn when the wind is too strong/weak
How oiling would affect the efficiency of the wind turbine
Efficiency would increase because amount of energy usually transferred would increase
Reduce friction
Why people should be encouraged to use energy efficient electrical devices
More efficient devices waste less energy
More efficient devices need lower energy input
Describe a method the student could use to determine the density of the rock
Fill a displacement can with water level with sprout
Place rock in water and collect displaced water
Measuring cylinder used to determine volume of displaced water
Volume or rock = volume of displaced water
Use of density = mass ➗ volume
The student determined the density of the rock to be 2.55 +- 0.10 g/cm’.
Maximum and minimum density of the rock
Maximum = 2.65 (g/cm3)
Minimum = 2.45 (g/cm3)
Which 2 types of rocks in Table 1 could be the type of rock the student had
Chalk or flint
Why taking the measurements more than once may improve the accuracy of the density value
A mean can be calculated which reduces effect of random errors
What equation links current, potential difference and power
Power = current x potential difference
P = V x I
Why the zero error is not important
Only the change in reading/mass being observed
What equation links efficiency, total power input and useful power output
Efficiency = useful power out ÷ total power
A student rubbed a plastic rod with a cloth.
The rod became negatively charged and the cloth became positively charged
Explain why the cloth became positively charged
Friction causes electrons to move from the rod and on to the cloth
The charge on the rod is positive, as it has lost electrons
The charge on the cloth is negative, as it has gained electrons
A negatively charged rod is held near an earthed conductor
Why does a spark jumps between the negatively charged rod and the earthed conductor
The large potential difference between the two objects causes negative electrons/charges to move through the air from the rod to the conductor
What does an alpha particle consist of
Two protons and two neutrons tightly bound together
Explain how the risk from internal contamination is different to the risk from external irradiation by a source of alpha radiation
Alpha radiation has a low penetrating power so external contamination will only act on an iradiated person’s skin
What measuring instrument should be used to measure the volume of water
A graduated cylinder or a burette
Some thermal energy was transferred to the surroundings while the water was being heated
Explain how this affected the student’s value for the specific latent heat of vaporisation of water
The transfer would result in a lower value
Some of the energy supplied to heat the water is lost to the environment
Some of the water evaporated before its temperature reached 100 °C.
Explain how this affected the student’s value for the specific latent heat of vaporisation of water
Less energy required for remaining water for phase change from liquid to gas
The braking distance of a car increases as the speed of the car increases
Give two other factors that increase the braking distance of a car
Wet/icy road conditions
Poor condition of brakes
Why the driver’s reaction time affects the thinking distance of a car
Longer reation time = longer distance
Which of the following conclusions can be made from figure F about reaction time of alcohol
Mean reaction time increases after drinking alcohol
Change in reaction time is not the same for all people after drinking alcohol
Why does hailstone accelerate
There is a resultant force acting
Why hailstone reaches terminal velocity
As velocity of hailstone increases air resistance increases
Until air resistance becomes equal to weight of the hailstone
Why does terminal velocity increase with mass
As mass increase weight of hailstone increase
Difference in maximum kinetic energy of a hailstone with a mass of 10g and hailstone mass 20g
Kinetic energy depends on mass and velocity
As mass increase so does terminal velocity
As mass doubles kinetic energy doubles
What’s the same as 1 joule
1Nm
Centre of mass
The point which weight may be considered to act
1 property of a spring that makes it suitable
Deforms elastically so will return to its original shape
