Grade 10 Physical Sciences · Mechanics

State energy laws and definitions

State energy definitions and laws in full, for example kinetic energy, gravitational potential energy or the law of conservation of mechanical energy.

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Mechanical Energy: Kinetic energy and Gravitational Potential energy IntroductionMiss Martins Maths and Science

[GRADE 10] Conservation of mechanical energyMaski

Conservation of Mechanical Energy - Physics #grade10Edu-ca-te

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Question 5.1 · May/June 2025 · Paper 1 · National (DBE) · 2 marks

Water is drawn from a water source

12, 5

m below the ground by an electric pump. The water is lifted vertically upwards at a constant speed, as shown in the simplified diagram below.

The pump lifts the water upwards at a rate of

2, 5

kg·s

^{- 1}

. Ignore ALL frictional and capillarity effects. Diagram for this question

5.1 Define the term non-conservative force.(2)

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More past paper questions: state energy laws and definitions

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3. Question 5.1 · November 2024 · Paper 1 · National (DBE) · 2 marks
A constant force F is applied at an angle of $30°$ to the horizontal on a crate of mass $6$ kg that is initially at rest, as shown in the diagram below.

A constant frictional force of $10$ N acts on the crate as it moves from rest at point A along a horizontal surface to point B. The distance between point A and point B is $1, 5$ m. The speed of the crate at point B is $2$ m·s $^{- 1}$ .
5.1 Define the term work done by a force.(2)
Show the memo (1 tick)Memo
1. ✓
  Definition of workThe work done on an object by a constant force F is $F Δ x cos θ$ , where F is the magnitude of the force, $Δ x$ the magnitude of the displacement and $θ$ the angle between the force and the displacement.
  
  OR
  
  The work done on an object is the product of the force and the displacement of the object in the direction of the displacement.
  2 marks · State energy laws and definitions
4. Question 5.1 · May/June 2024 · Paper 1 · National (DBE) · 2 marks
A crate of mass $18$ kg, initially at rest, slides down a frictionless slope from point A to point B. The crate then moves along a rough horizontal surface from point B towards point C. Point A is $3$ m above the horizontal surface. See the diagram below.
5.1 State the principle of conservation of mechanical energy in words.(2)
Show the memo (1 tick)Memo
1. ✓
  Principle of conservation of mechanical energyThe total mechanical energy/sum of the gravitational potential energy and kinetic energy/sum of $E_{p}$ and $E_{k}$ in an isolated system is conserved/remains constant.
  
  OR
  
  If the sum of the non-conservative forces is zero, then total mechanical energy/sum of the gravitational potential energy and kinetic energy/sum of $E_{p}$ and $E_{k}$ is conserved/remains constant.
  2 marks · State energy laws and definitions
5. Question 4.1 · November 2024 · Paper 1 · National (DBE) · 2 marks
Two trolleys, A and B, of masses of $1, 5$ kg and $2$ kg respectively, are held in a stationary position on a straight, horizontal, frictionless track, with a compressed spring between them. The trolleys are released and the spring takes t seconds to return to its natural length. The spring then falls to the ground.
Trolley A moves to the left, while trolley B moves to the right and then up a frictionless inclined plane, rising to a maximum vertical height of $1, 5$ m, as shown in the diagram below.

Ignore the rotational effects of the wheels.
4.1 Write down the principle of conservation of mechanical energy in words.(2)
Show the memo (1 tick)Memo
1. ✓
  Principle of conservation of mechanical energyThe total mechanical energy/sum of gravitational potential energy and kinetic energy, in an isolated system remains constant/is conserved.
  2 marks · State energy laws and definitions
6. Question 5.1 · May/June 2023 · Paper 1 · National (DBE) · 2 marks
An electric motor pulls a $20$ kg crate from rest at point A up an inclined plane by means of a light inextensible rope. The inclined plane makes an angle of $18°$ with the horizontal. B, C and D are points on the inclined plane and the distance between points A and C is $15, 6$ m, as shown in the diagram below.

The motor exerts a constant force of $96, 8$ N parallel to the inclined plane on the rope.

A constant frictional force of $13, 5$ N acts on the crate as it moves on the inclined plane.
5.1 Define a non-conservative force.(2)
Show the memo (1 tick)Memo
1. ✓
  Definition of a non-conservative forceA force is non-conservative if the work it does/done on an object which is moving between two points depends on the path taken.
  
  OR
  
  A force is non-conservative if the work it does/done in moving an object around a closed path is non-zero.
  2 marks · State energy laws and definitions

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