General physics Flashcards
Explain why the force on the ship due to the ship’s engine is greater than the value you calculated [1]
water resistance
Car travels with constant speed, V. Driver sees obstacle on road ahead.
distance travelled in the time betweent he driver seeing the obstruction and applying the brakes is the thinking distance.
a) Explain why the thinking distance is directly proportional to v. [1]
thinking time is constant as v=d/t
When brakes are applied, car deccelerates uniformly to rest. Frictional force applied by brakes is constant. Distance travelled between first applying the brakes and the car stopping is the braking distance.
b) explain why the braking distance is proportional to v^2 [3]
kinetic energy
Ek=0.5mv^2
work done=fd=Ek d=(0.5m/f)v^2
Explain why opening the parachute cannot reduce the speed of the skydiver to zero [2]
at zero speed no air resistance
weight still acts
Explain, in terms of the work done, the energy change that takes place as the trolley slows down [3]
work done against friction
ke to zero
thermal energy produced
Explain, in terms of molecules, why liquids are very difficult to compress [2]
molecules close
repulsive forces large
Burning waste materials from farm crops generates electricity.
State and explain whether this process is renewable [2]
renewable
crops can be regrown
State two environmental consequences of burning coal to generate elecctricity [2]
air pollution
greenhouse gas
When angle of ramp is increased, state what happens to the trolley’s motion, moving at constant speed [2]
speed increases
resultant force acting on trolley
Explain, in terms of molecules, why gases expand more than liquids [2]
average distance between molecules greater
forces between molecules lower
Describe what happens to the velocity of the ball as it accelerates downwards uniformly [2]
velocity increases with time
at a constant rate
State and explain which feature of a speed-time graph shows acceleration [2]
gradient
change in speed/time
Train took 80s to reduce speed from 84 to 42, explain why it takes more time to reduce from 42 to 0 [1]
air resistance less
Piston released and moves to right, hot gas in piston. Explain why [2]
pressure falls volume increases
initially larger pressure inside than outside
Explain why pressure in a balloon is smaller on ground than in atmosphere, volume increases as rises. [2]
fewer atoms per unit volume
rate of collision dec
