Paper 2 PPQs Flashcards
Some dots, which represent galaxies, were marked on a balloon. The balloon was then inflated. Give one strength and 2 weaknesses of this model in representing the idea of an expanding Universe.
- as the balloon expands the dots get further apart, representing the galaxies moving apart
- dots are only on the surface of the balloon, galaxies are throughout the universe
- there is a limit to how far the balloon can expand
The Big Bang theory is one model used to explain the origin of the universe. How does the Big Bang theory describe the universe when it began?
extremely hot and dense
The Big Bang theory suggested that gravity would slow the rate at which galaxies move away from the Earth. New observations suggest that distant galaxies are moving away from the Earth at an increasingly fast rate. What do the new observations suggest is happening to the universe?
it is expanding at an ever greater rate
give some reasons why peer review is an important process.
- detects false claims
- detects bias
- detects inaccurate data
Give 2 ways that the historical model of the solar system is different from what we now know about the solar system and 2 ways that it is the same as what we now know about the solar system.
- differences: old model showed earth at centre of solar system, which it is not; old model showed fewer planets
- similarities: in both, planets have circular orbits; both shows the moon as in orbit around the earth
Describe the orbit of an artificial satellite and why it is like this
circular - balances its forward motion with the pull of gravity.
The Universe now contains a large variety of different elements. Describe how this happened.
- fusion takes place within stars
- hydrogen formed into helium
- fusion continued and formed larger elements
- elements heavier than iron were formed in supernova
- heavy elements were scattered by the supernova explosion.
How does the red-shift from distant galaxies provide evidence for the beginning of the Universe?
- red-shift shows galaxies are moving away from the Earth
- more distant galaxies show bigger red-shift
- distant galaxies are moving away faster
- this suggests the universe started from a single point
Explain, in as much detail as you can, the scientific evidence for the ‘Big Bang’ theory of the origin of the Universe.
Observations of galaxies show a red-shift - light appears to be shifted towards the red end of the spectrum. More distant galaxies show a bigger red-shift. The red-shift shows that the galaxies are moving away from each other, and more distant galaxies are moving away faster. Therefore, the Universe is expanding. If this is the case then all matter in the Universe once started from a single point.
an orbiter is the reusable part of a space shuttle. What name is given to the force which keeps the orbiter in orbit around the Earth?
gravity
a skateboarder jumps forwards off his skateboard. The skateboard is stationary at the moment the skateboarder jumps. The skateboard moves backwards as the skateboarder jumps forwards. Explain, using the idea of momentum, why the skateboard moves backwards.
The principle of conservation of momentum states that total momentum before an event is equal to the total momentum after. The total momentum before the skateboarder jumps off is 0, therefore the total momentum after they jump must also be 0. After jumping, the skateboarder has forwards momentum so the skateboard must have equal momentum in the opposite direction (backwards).
A dog has its lead pulled by its owner. Despite the force applied by the owner, the dog is not moving. Explain why no work is done on trying to move the dog.
the dog is pulling in an equal and opposite direction. Work only occurs if a force is applied over a distance (W=fs) and as the distance moved is 0, so the work done is 0
In a dynamo operated torch, the handle is turned to generate an electric current which charges a battery. The torch has a traditional light bulb which lights when the current runs through it. Suggest 3 ways to improve the efficiency of the torch.
- use LEDs instead of light bulbs as they are more efficient to reduce heat losses
- increase turns on electromagnet in transformer to increase the current generated from turning the handle
- reduce friction to reduce heat loss
A racing driver is driving his car along a straight and level road and pushes the accelerator pedal as far down as possible. The car does not accelerate above a certain maximum speed. Explain the reasons for this in terms of the forces acting on the car.
There is a maximum forward force and the drag/friction/resistance increases with speed until the forward and backward forces are equal so there is no net force/acceleration
When a ball reaches a batsman it is travelling at 30m/s . The batsman strikes the ball which moves off at 30m/s in the opposite direction. The ball has a mass of 0.16 kg. Calculate the change in momentum of the ball
For questions like this, it is good to refer to the ‘opposite direction’ as a negative. So if you’ve got 30 m/s in one direction, the opposite would be -30 m/s. 0.16 * 30 = 4.8 kg m/s and 0.16 * -30 = -4.8 kg m/s So 4.8 - -4.8 = 9.6 kg m/s
