Grade 11 Physical Sciences · Mechanics

Draw a free-body or force diagram

Draw every force acting on an object as a labelled arrow, for example weight, normal force, friction and applied force on a box.

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Question 5.3 · November 2025 · Paper 1 · National (DBE) · 3 marks

A crate of mass

3

kg is at rest at point A on a frictionless horizontal surface. A constant horizontal force F of

12

N acts on the crate and moves it from point A to point B. The crate then moves down a rough plane, inclined at

20°

to the horizontal. The distance from point A to point B is

7

m and from point B to point C is

6, 8

m, as shown in the diagram below. Diagram for this question

Force F is removed when the crate reaches point B. The crate then experiences a constant frictional force of

21

N as it moves down the incline.

5.3 Draw a free-body diagram showing ALL the forces acting on the crate as it moves down the incline.(3)

Work it out on paper first. Then mark yourself with the official memo, one tick at a time.

More past paper questions: draw a free-body or force diagram

Work each one out first, then open the memo and check every tick.

3. Question 7.2.2 · May/June 2025 · Paper 1 · National (DBE) · 3 marks
7.2 Sphere S is attached to the ceiling at point P by a light inextensible string. When sphere R, on an insulated stand, is brought close to sphere S they repel and sphere S comes to rest with the horizontal distance between the centres of the spheres equal to $0, 03$ m.

Sphere R is directly below point P. The string makes an angle θ with the vertical, as shown in the diagram below.

Answer the questions that follow.
7.2.2 Draw a labelled free-body diagram showing ALL the forces acting on sphere S when it is at rest.(3)
Show the memo (3 ticks)Memo
1. ✓
  WeightA dot with an arrow vertically downwards, labelled w.
  
  Accepted labels: $F_{w}$ / $F_{g}$ / mg / $1, 47 \times 1 0^{- 3}$ N / gravitational force / weight.
  1 mark · Draw a free-body or force diagram
2. ✓
  Electrostatic forceAn arrow from the dot horizontally to the right (away from R), labelled $F_{E}$ .
  
  Accepted labels: F / Electrostatic force / Coulomb force / $F_{R o n S}$ .
  1 mark · Draw a free-body or force diagram
3. ✓
  TensionAn arrow from the dot along the string towards P (up and to the left), labelled T.
  
  Accepted labels: $F_{T}$ / $F_{s t r in g}$ / tension.
  1 mark · Draw a free-body or force diagram
4. Question 2.2 · November 2025 · Paper 1 · National (DBE) · 4 marks
A block of mass $5$ kg is at rest on a rough horizontal surface. When a constant force F of magnitude $18$ N acts on the block at an angle $θ$ to the horizontal, the block experiences maximum static friction. See the diagram below.
2.2 Draw a labelled free-body diagram showing ALL the forces acting on the block.(4)
Show the memo (4 ticks)Memo
1. ✓
  Normal forceAn arrow pointing vertically UP from the dot, labelled N.
  
  Accepted labels: N, $F_{N}$ , Normal (force), $F_{n or ma l}$ .
  1 mark · Draw a free-body or force diagram
2. ✓
  Applied force FAn arrow from the dot pointing up and to the right at angle $θ$ to the horizontal, labelled F.
  
  Accepted labels: F, $F_{A}$ , $18$ N, Applied force.
  1 mark · Draw a free-body or force diagram
3. ✓
  Static frictionAn arrow from the dot pointing horizontally to the LEFT, labelled $f_{s}^{ma x}$ .
  
  Accepted labels: $f_{s}^{ma x}$ , $F_{f}$ , $f_{s}$ , f, Friction (force), (static) friction.
  
  $f_{k}$ is NOT accepted as a label.
  1 mark · Draw a free-body or force diagram
4. ✓
  WeightAn arrow from the dot pointing vertically DOWN, labelled w.
  
  Accepted labels: w, $F_{g}$ , $F_{w}$ , $F_{e a r t h o n P}$ , weight, mg, $49$ N, gravitational force.
  1 mark · Draw a free-body or force diagram
5. Question 2.2 · November 2024 · Paper 1 · National (DBE) · 2 marks
In an experiment, a crate of mass $8, 5$ kg, lying stationary on a rough horizontal table, is connected to a mass hanger by means of a light inextensible string passing over a frictionless pulley, as shown in the diagram below. Mass pieces are added to the mass hanger and the acceleration of the crate is measured. The experiment is repeated several times by adding different masses to increase the hanging mass each time.

Ignore the effects of air friction.

The results obtained were used to draw the sketch graph below.
2.2 Draw a labelled free-body diagram showing ALL the HORIZONTAL forces acting on the crate JUST BEFORE it starts moving.(2)
Show the memo (2 ticks)Memo
1. ✓
  Static frictionAn arrow from the dot pointing LEFT (away from the pulley), labelled $f_{s}$ .
  
  Accepted labels: $f_{s}$ / static friction / $f$ / $F_{f}$ .
  1 mark · Draw a free-body or force diagram
2. ✓
  TensionAn arrow from the dot pointing RIGHT (towards the pulley), labelled $T$ .
  
  Accepted labels: $T$ / $F_{T}$ / $F_{s t r in g}$ / tension.
  1 mark · Draw a free-body or force diagram
6. Question 2.2 · May/June 2024 · Paper 1 · National (DBE) · 5 marks
Block A of mass $4, 1$ kg is connected to block B of mass $2, 3$ kg by a light inextensible string passing over a frictionless pulley. Block A is at rest on a rough horizontal table and block B hangs vertically, as shown in the diagram below.

A force F of magnitude $49$ N is applied on block A at an angle of $50°$ to the horizontal, causing block A to accelerate TO THE LEFT from rest along the table.

The coefficient of kinetic friction between the surface of the table and block A is $0, 35$ .
2.2 Draw a labelled free-body diagram showing all the forces acting on block A while it accelerates to the left.(5)
Show the memo (5 ticks)Memo
1. ✓
  WeightArrow straight down from the dot, labelled w.
  
  Accepted labels: $F_{g}$ , $F_{w}$ , $40, 18$ N, mg, weight, gravitational force.
  1 mark · Draw a free-body or force diagram
2. ✓
  Normal forceArrow straight up from the dot, labelled N.
  
  Accepted labels: $F_{N}$ , Normal, $F_{n or ma l}$ .
  1 mark · Draw a free-body or force diagram
3. ✓
  Applied forceArrow from the dot pointing up and to the LEFT at $50°$ to the horizontal, labelled F.
  
  Accepted labels: $F_{a pp}$ , $49$ N, $F_{a}$ , $F_{A}$ .
  1 mark · Draw a free-body or force diagram
4. ✓
  Kinetic frictionArrow from the dot pointing to the RIGHT, labelled f.
  
  Accepted labels: (kinetic) friction, $F_{f}$ , $f_{k}$ , $f_{r}$ .
  1 mark · Draw a free-body or force diagram
5. ✓
  TensionArrow from the dot pointing to the RIGHT, labelled T.
  
  Accepted labels: $F_{T}$ , tension, $F_{s t r in g}$ .
  1 mark · Draw a free-body or force diagram

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