1.Basic Flashcards
U13PH4 State the principle of conservation of momentum.
The [vector] sum of the momenta of bodies [in a system] stays constant [even if forces act between the bodies] provided there is no external [resultant] force.
C3 11. (a) A golfer prepares to take a shot. Explain clearly how the golfer achieves a stable position in order to take the shot. [2]
Both feet apart and in line (1)
Centre of gravity acts between both feet (1)
C3 (d) (i) In reality a golfer strikes the ball with large amounts of backspin. Explain how applying backspin will affect the mean distance travelled by the ball. Justify your answers by referring to the forces acting on the ball during the flight and how the ball lands. The effects of the air should be considered for this part. [4]
Forces clearly identified as lift, drag and weight (1)
Backspin provides more lift↑ or equivalent e.g. air pressure reduced behind the ball (1)
Description of ball landing e.g. ball spins back or stops suddenly so ball will not travel far on landing (or roll forward)(1)
Well argued conclusion (1)
A09PH1 5. A ball of mass 0·60kg is dropped from the top of a building 80m high. (ii) Explain, referring to molecules, what has happened to this ‘missing’ energy. [2]
Air molecules gain kinetic energy (1) Molecules of ball gain kinetic energy (1) [accept internal energy of ball increases]. [Accept “heat” instead of KE for one of the marks only]
A09PH1 (iii) Explain in terms of the kinetic energy of the water why the turbine is not 100% efficient. [1]
Not all of Ek [accept: energy] of water used by turbine / water retains some Ek after passing through turbine [Note: This reason predominates – responses involving wastage through Ek transfer to other forms not credited.]
A09PH1 (II) Suggest one advantage of choosing the tidal stream option. [1]
Out of sight (no visual impact)
Regular / predictable energy generator
Little environmental impact
Fewer turbines so less materials/maintenance
Less noise pollution
U16PH4 (i) Newton’s second law of motion; [2] (ii) the principle of conservation of momentum. [2]
The rate of change of momentum of an object is (directly) proportional to the resultant / net / total / overall (1) force acting on it (1) [and is in the direction of that force] Award 1 mark for stating F = ma with all terms correctly
The [vector sum of the] momenta of bodies in a system stays constant (1) [even if forces act between the bodies], provided there is no [net] external [resultant] force / isolated system (1)
I. Explain what is meant by the moment of inertia. [2]
I. The (sum of) the products of mass times distance squared (1) from axis (of rotation of the ball) (1)
(i) Explain clearly by what factor the drag force changes for these two cross-sectional areas. [3]
1/2𝜌𝐴𝑣2𝐶𝐷 used (1)
Stating 𝜌𝑣2𝐶𝐷 remain constant (can be implied) (1)
Drag force [increased] - factor of 5.04 for end over end (1) Or drag force factor 5.04 [less] for spin type kick
(ii) If the rugby ball had been kicked in a region where the density of the air is lower, explain how your answer Drag Force would change, if at all. [2]
The values of CD, speed and A stay the same for different altitude (1)
Factor would not change (1)
A:GPE=max KE=0 EPE=0
B:GPE↓ KE↑ EPE=0
C:GPE↓ EPE↑ KE↑&↓
D: EPE=max GPE=min KE=0
