Forces and Motion — Year 12 Physics

AS91524 | Level 3 NCEA Physics | Mechanics Revision & Application

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📋 Worksheet 1: Key Mechanics Concepts — Revision

Revise the foundational concepts needed for AS91524 problem-solving.

1. State Newton's Three Laws of Motion in your own words.

First Law (Inertia):

Second Law (F = ma):

Third Law (Action–Reaction):

2. Match each force type to its correct description by writing the letter in the blank.

A. Weight (gravity)

B. Normal force

C. Friction

D. Tension

____ Acts perpendicular to a surface, pushing objects apart.

____ A pulling force transmitted through a rope or cable.

____ Acts downward due to Earth's gravitational pull (F = mg).

____ Opposes relative motion between surfaces in contact.

3. Describe a real-world scenario where you observe Newton's Third Law in action. Provide details about the forces involved.

4. Create a hands-on activity: Design an experiment to demonstrate the concept of friction. Describe the materials you would use and the steps you would take.

5. Write the kinematic equation that links displacement (s), initial velocity (u), acceleration (a), and time (t). Then state what each symbol represents.

Equation: ___________________________________

🔧 Worksheet 2: Mechanical Systems — Diagram & Force Labelling

Label forces and apply free-body diagram conventions for AS91524.

6. Inclined Plane: A 12 kg box sits on a smooth ramp inclined at 30° to the horizontal.

In the space below, draw a free-body diagram of the box on the inclined plane. Label the following forces with arrows and correct notation:

Weight (W = mg), acting vertically downward

Normal force (N), perpendicular to the ramp surface

Component of weight parallel to the ramp (W sin θ)

Component of weight perpendicular to the ramp (W cos θ)

Calculate the magnitude of the normal force acting on the box. Show all working steps. (g = 9.8 m/s²)

7. Simple Pulley System: A pulley is used to lift a 25 kg load. The rope is pulled with a force T.

Draw and label a free-body diagram of the hanging load below. Include all forces acting on it.

Problem-Solving Steps: If the load accelerates upward at 1.5 m/s², calculate the tension T in the rope.

Step 1 — Identify forces and direction of acceleration:

Step 2 — Apply Newton's Second Law (ΣF = ma):

Step 3 — State your answer with correct units:

T = _____________________ N

⚙️ Worksheet 3: Scaffolded Problem Solving

Apply Newton's Second Law, kinematics, and motion graph interpretation. Show ALL working — this is required for AS91524.

8. A ski-lift gondola of mass 450 kg starts from rest and reaches a speed of 3.6 m/s in 8 seconds along a slope inclined at 15° to the horizontal. The frictional force on the gondola is 180 N.

(a) Calculate the acceleration of the gondola.

(b) Draw a free-body diagram of the gondola on the slope, labelling all forces.

(c) Using Newton's Second Law, calculate the driving force (tension) in the cable. (g = 9.8 m/s²)

9. A construction crane lifts a 320 kg steel beam from rest. The beam accelerates upward at 0.75 m/s² for 6 seconds, then moves at constant velocity for a further 10 seconds.

(a) Calculate the tension in the crane cable during the acceleration phase.

(b) On the axes below, sketch a free-body diagram for the beam during the acceleration phase. Label all forces.

(c) Use your understanding of forces to explain how the crane operates effectively in lifting heavy loads.

10. A 1,200 kg car travelling at 20 m/s brakes to a stop over a distance of 50 metres on a flat road.

(a) Calculate the deceleration of the car.

(b) Calculate the braking force applied.

(c) If the road were wet and friction reduced by 30%, how would this affect stopping distance? Explain using Newton's Second Law.

💭 Worksheet 4: Reflect and Connect

Consolidate your learning and prepare for AS91524 assessment.

11. Write two key takeaways from today's lesson — concepts or problem-solving strategies you now feel more confident about.

Takeaway 1:

Takeaway 2:

12. Write one question you still have about forces, motion, or mechanical systems that you would like clarified before your AS91524 assessment.

13. Rate your confidence with each skill below by ticking the appropriate box.

Drawing and interpreting free-body diagrams:

Not yet confident

Getting there

Confident

Applying Newton's Second Law (ΣF = ma) to solve problems:

Not yet confident

Getting there

Confident

Using kinematic equations to find unknown quantities:

Not yet confident

Getting there

Confident

Sketching and interpreting velocity–time graphs:

Not yet confident

Getting there

Confident

Solving multi-step mechanics problems (AS91524 style):

Not yet confident

Getting there

Confident

Teacher reminder: Always show all working steps, use correct units, and apply Newton's laws systematically — this is essential for achieving Merit and Excellence in AS91524.