Describe, in terms of the forces acting on the sky-diver, her motion between leaving the balloon and opening her parachute
any two from: (2)
- weight OR force of / due to gravity acts down
- (force of / due to) air resistance / drag / friction acts up / opposes motion
- initially / up to 10 s: resultant force is downward OR downward force is greater than upward force
- resultant force causes acceleration
air resistance increases as speed increases / she accelerates
- acceleration (down) initially / for first 10 s
- acceleration decreases as air resistance increases / resultant force decreases
- zero acceleration / constant speed / terminal velocity reached when upwards force = downwards force OR when no / zero resultant OR when forces balanced OR when downward force = air resistance
- terminal velocity / constant speed reached after (about) 10 s OR at 60m/s
State what is meant by limit of proportionality
beyond where the extension is not directly proportional to the load OR
(point) where extension stops being directly proportional to the load OR
point up to which extension is directly proportional to the load
In terms of momentum of molecules, explain how a gas exerts pressure on the walls of its container.
molecules strike walls
momentum (of molecules) changes / momentum = mass × velocity
force = rate of change of momentum
pressure = (sum of) force(s) / area OR pressure = rate of change of momentum / area
Describe how the geothermal power station generates electricity.
water is heated / changed to steam as it passes through (fractures in) rocks (1)
steam turns a turbine (1)
the turbine drives a generator (1)
generator produces electricity (1)
Zuletzt geändertvor einem Jahr