6 exam-style questions with full mark schemes and model answers. Write your own answer and the AI examiner marks it against the mark scheme.
Learn this properly: Stopping DistancesOur Sun is a main-sequence star of about average size. In the very distant future it will change and eventually die.
Describe the life cycle of a star like the Sun, from its birth to its final stage. In your answer you should name the main stages in the correct order and describe what happens at each stage. (6 marks)
A car of mass 1200 kg is moving in a straight line along a level road at a velocity of 15 m/s.
(a) Calculate the momentum of the moving car. Use p=mv. Show your working and give the unit. (2 marks)
(b) This car runs into the back of a stationary car of mass 800 kg, and the two cars lock together and move off as one. Using conservation of momentum, calculate the velocity of the two cars immediately after the collision. Show your working. (2 marks)
(Higher tier.) A loaded trolley of mass 2.0 kg is moving at 6.0 m/s when it strikes a buffer and is brought to rest in a time of 0.50 s.
(a) Calculate the size of the average force the buffer exerts on the trolley. Use F=ΔtΔp, where Δp is the change in momentum. Show your working and give the unit. (2 marks)
(b) Modern buffers and car "crumple zones" are designed to increase the stopping time. Explain how a longer stopping time makes a collision safer. (1 mark)
The stopping distance of a car is made up of two parts.
(a) Name the two parts that add together to give the total stopping distance. (1 mark)
(b) When a car's speed doubles, its braking distance becomes about four times as large, even though the braking force is the same. Explain why the braking distance increases by so much more than the speed. (2 marks)
The national grid uses transformers to transmit electrical power across the country at a very high voltage and therefore a low current.
Explain why transmitting electricity at a low current reduces the amount of energy wasted in the transmission cables. (2 marks)
Light from distant galaxies is observed to be red-shifted: the wavelength of the light is shifted towards the red (longer-wavelength) end of the spectrum, and more distant galaxies show a greater red-shift.
State what this observation tells us about the Universe. (1 mark)