Past Paper Points that missed Flashcards
Explain why the minimum force needed to close the computer is likely to be less than 4.2N. (2)
- The lid is pulled down by its weight and the force of gravity. - Acts in same direction as closing force, anticlockwise.
How to find the distance of an object in a mirror?
Look down sighting pins line is drawn through the mirror . A line is also drawn from the object directly to the mirror. The lines should cross behind the mirror, here is the position of the object.
When finding the distance of an object in a mirror, describe how the student can be able to confirm that the position of the image is correct. (2)
- Measure distances to mirror - Object distance = image distance.
Statements that are correct about a mirror? (2)
- The image in a plane mirror is virtual - The angle of incidence equals the angle of reflection.
If 200J of energy is put in and 1800J is useful and 200J is lost to surroundings how efficient is the devise?
- 0.9
Why does a heating element is a kettle get hot when its electrical supply is switched on? (2)
- Energy from the supply of electrical energy is transferred to thermal energy. - The transfer to thermal energy vibrates the particles in the water. The current is causing a heating effect in the element as there is a resistance.
Why have a fuse at a specific value just over the normal? (2)
Only one above working current. When the current goes over the specified value there is no delay, the fuse will just blow.
2 mA in A?
0.002 Amps
Ways to check experiment data is accurate with measuring cylinder and balance?(2)
- Check balance is zero. - Measure from bottom of meniscus.
Coffee cups exam question (4) - Cups are same size one has more coffee in, compare pressures in the coffee at the bottom of each cup?
- Pressure greater in the full cup, less in the half full cup. - reference to pressure equation p = W / A - depth/mass/weight of liquid different in each cup. - density of liquid is the same in each cup.
The energy from the beta radiation is expected to destroy the cells in the tumor over a period of weeks, what would be the most suitable half-life of the isotope. 75 mins, 75 hours, 75 days, 75 years. EXPLAIN CHOICE!
75 days. - The isotope will last for long enough. - A and B may need to be replaced.
A straight line graph is a……
Linear Graph
A curved line graph is a….
Non-Linear
Describing an experiment….
Equation measuring detail of measurement e.g 50m repeat/averaged how to make measurement
LDR?
- In the dark and at low light levels, the resistance of an LDR is high, and little current can flow through it. - In bright light, the resistance of an LDR is low, and more current can flow through it. NON-LINEAR
Thermister?
- At low temperatures, the resistance of a thermistor is high, and little current can flow through them. - At high temperatures, the resistance of a thermistor is low, and more current can flow through them.
Explain why a voltage is induced?
Wire cuts magnetic field lines.
One way to increase voltage?
STRONGER magnet
When question mentions energy transfer….
Mention efficiency equation. efficiency = useful energy output / total energy input
1 watt is the same as……
1 Joules / per second
How many W in Kw
1000W
Newtons 1st Law
The First Law states that objects with balanced forces acting on them will stay at rest, or in constant motion.
Newtons 2nd law
F=ma
Hooke’s Law
The extension of an elastic object is directly proportional to the force applied to it: F=KE
reason for acceleration change in car?
Increased Friction Increased Air resistance GRAPH IS NON-LINEAR
electronic balance measures……
mass
when does a uniform magnetic field occur?
Two opposite poles brought close together. Magnetic field lines and parallel and move from north to south
Explain how to produce a uniform magnetic field?
- Two permanent bar magnets. - Poles arranged correctly, North facing south - Idea of magnets being the correct distance apart