Physics - annotated exemplars level 1 AS90936

Demonstrate understanding of the physics of an application (1.2)

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Low Excellence

Commentary
Student response

Student 1 (PDF, 37KB)

For Excellence, the student needs to demonstrate comprehensive understanding of the physics of an application. 

This involves linking ideas to integrate the relevant physics of the chosen application with its use, and may involve explaining, elaborating, justifying, relating, evaluating, comparing and contrasting, or analysing.

The student has demonstrated comprehensive understanding by explaining the workings of a generator, and linking the kinetic energy input to the generator to the electrical energy output from the generator (1) (2).

The student has attempted to explain the basic working of the wind turbine (3) (4), and has attempted to explain why the turbine is not totally efficient (5) (6).

To reach Excellence more securely, the student could have:

  • given a much clearer link between the spinning of the blades, the spinning of the generator and the spinning of the coil of wire in the magnetic field of the magnets
  • made it clear that energy lost by friction is heat energy
  • given a clearer explanation of the role of friction in the resistance of a wire, by recognising that the resistance of copper wire is caused by friction, not the other way around.

High Merit

Commentary
Student response

Student 2 (PDF, 36KB)

For Merit, the student needs to demonstrate in-depth understanding of the physics of an application.

This involves explaining how or why the physics applies to the use of the chosen application.

In-depth understanding is demonstrated in this account of the forces that act on a skydiver. The student has explained how terminal velocity is reached before the parachute is opened (1); why the force of air resistance depends on the surface area of the parachute (4); why the speed decreases after the parachute has been opened (2); and why terminal velocity is reached after the parachute is opened (3).

To reach Excellence, the student would need to demonstrate comprehensive understanding of the physics of the chosen application. This involves linking ideas to integrate the relevant physics of the application with its use. Refer to Explanatory Note 4.

The student could have done this by:

  • linking the size of the air resistance force to the speed at which the skydiver is falling
  • linking the greater cross-sectional area of the parachute to a greater drag for the same speed, and comparing this to the force due to gravity remaining the same
  • explaining that the unbalanced force upwards causes speed to decrease, which causes drag to decrease; that speed continues to change until the drag force upwards becomes equal in size to the downwards force due to gravity, providing some values of the parachute sizes and speeds involved
  • analysing graphs of speed and force versus time for a skydiver.

Low Merit

Commentary
Student response

Student 3 (PDF, 35KB)

For Merit, the student needs to demonstrate in-depth understanding of the physics of an application.

This involves explaining how or why the physics applies to the use of the chosen application.

The student has demonstrated in-depth understanding by explaining conservation of angular momentum in terms of a spinning skater (1), and they have attempted to explain how the force of the skate pushing against the ice creates the motion of the skater (2).

For a more secure Merit, the student could have:

  • given a clearer explanation of the role friction plays in how the skater starts moving and continues to move
  • explained how a force applied at an angle can create forward motion.

High Achieved

Commentary
Student response

Student 4 (PDF, 36KB)

For Achieved, the student needs to demonstrate understanding of the physics of an application.

This involves providing characteristics of, or an account of, the physics related to the use of the chosen application.

The student has demonstrated understanding with a good descriptive account of the forces acting on a skydiver when they are descending to the ground (1) (2).

The student has attempted to provide characteristics with their explanation of why a terminal velocity is reached, firstly after they have jumped (3) and secondly after the parachute has been opened (4). The student has also attempted to explain why air resistance depends on the surface area of the object that is falling (5).

To reach Merit, the student would need to demonstrate in-depth understanding of the chosen application. This involves explaining how or why the physics applies to the use of the application.

The student could have:

  • explained why a terminal velocity is reached based on the need for balanced (not zero) forces, and how air resistance changing with respect to gravity can achieve this
  • explained more clearly why surface area affects air resistance.

Low Achieved

Commentary
Student response

Student 5 (PDF, 31KB)

For Achieved, the student needs to demonstrate understanding of the physics of an application.

This involves providing characteristics of, or an account of, the physics related to the use of the chosen application.

The student has demonstrated understanding with a good descriptive account of the forces acting on a skydiver when they are descending to the ground (1).

The student has attempted to provide characteristics with their explanation of why a terminal velocity is reached, firstly after they have jumped (3) and secondly after the parachute has been opened (2), (4).

For a more secure Achieved, the student would need to describe further aspects related to the physics of the chosen application.

The student could have:

  • described the effect of the surface area of the parachute on air resistance
  • described how air resistance increases as the parachutist falls.

High Not Achieved

Commentary
Student response

Student 6 (PDF, 32KB)

For Achieved, the student needs to demonstrate understanding of the physics of an application.

This involves providing characteristics of, or an account of, the physics related to the use of the chosen application.

The student has attempted to relate the way that a wind turbine works to the relevant physics, by describing the energy changes that take place (1).

To reach Achieved, the student would need to describe further aspects related to the physics of the chosen application.

The student could have:

  • described the workings of an electrical generator in more detail
  • described the physics involved in the transformation of kinetic energy into electrical energy.
 
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