What to Investigate

Newton's First Law states that an object remains at rest or continues moving with constant velocity unless acted upon by an external force. This property is called inertia — the tendency of objects to resist changes in their state of motion.

Investigation Steps

1. Gather materials: A small toy car, a smooth flat surface (table or floor), a book, and some coins or small blocks.
2. Test 1 - Inertia of rest: Place the book flat on a table. Quickly pull the book horizontally. Observe what happens to a coin placed on top of the book. The coin falls backward because it tends to stay at rest while the book moves.
3. Test 2 - Inertia of motion: Push the toy car along the smooth surface so it moves at constant speed. Suddenly stop the car with your hand. Observe what happens to a small block placed loosely on top. The block continues moving forward due to inertia.
4. Record observations: Note how long the car takes to stop with different surfaces. This relates to friction (covered next).

Expected Results

• Objects at rest stay at rest until a force acts on them.
• Moving objects continue moving until a force (like friction) stops them.
• Heavier objects (more mass) show more inertia — they are harder to start or stop.

What to Investigate

Equilibrium occurs when a body is balanced. For an object to be in equilibrium:

• The sum of forces in one direction equals the sum of forces in the opposite direction.
• The sum of clockwise moments equals the sum of anticlockwise moments (Principle of Moments).

Investigation Steps

1. Gather materials: A meter rule, a triangular block or eraser (fulcrum), some weights (small bags with stones or coins), and a string.
2. Balance the meter rule: Place the triangular block under the center of the meter rule. Adjust until the rule balances horizontally.
3. Test stability: Gently push one end of the rule down and release. Observe whether it returns to the original position (stable), moves further (unstable), or stays in the new position (neutral).
4. Test Principle of Moments: Hang a weight on one side of the rule. Move the fulcrum until it balances again. Record the distances from the fulcrum.

Types of Equilibrium

• Stable: Object returns to original position when displaced (e.g., a book standing upright)
• Unstable: Object moves further away when displaced (e.g., a pencil balanced on its tip)
• Neutral: Object stays in new position when displaced (e.g., a ball on a flat table)

Factors Affecting Stability

• Lower center of gravity: Wider base and lower center of gravity = more stable
• Widening the base: Provides more resistance to tipping

What to Investigate

Friction is the force that opposes motion between surfaces in contact. It depends on:

• The nature of the surfaces (rough or smooth)
• The normal force pressing the surfaces together

Investigation Steps

1. Gather materials: A wooden block, a spring balance (or elastic string with known strength), different surfaces (smooth table, rough carpet, sandpaper), and a flat surface.
2. Measure friction force: Attach the spring balance to the block. Pull horizontally at constant speed. The reading on the balance equals the friction force.
3. Test different surfaces: Repeat on each surface. Record the force needed to keep the block moving at constant speed.
4. Test normal force: Stack additional blocks on top and measure friction again. More weight = more friction.

Reducing Friction

You can investigate methods to reduce friction:

• Polishing: Sand the surface and test again
• Lubrication: Apply oil or grease between surfaces
• Use of rollers or wheels: Replace sliding with rolling

Worked Example

A wooden block of mass 2 kg is placed on a horizontal table. The coefficient of friction is 0.3. Calculate the friction force.

Solution: $F = \mu N$ $N = mg = 2 \text{ kg} \times 10 \text{ m/s}^2 = 20 \text{ N}$ $F = 0.3 \times 20 \text{ N} = 6 \text{ N}$

The friction force is 6 N. You need more than 6 N to start moving the block.

What to Investigate

A lever is a rigid body that turns about a fixed point called the fulcrum. It helps us multiply force or increase speed and distance.

Investigation Steps

1. Gather materials: A meter rule (lever), a triangular block (fulcrum), a weight to lift (small bag with stones), and a spring balance.
2. Set up first-class lever: Place the fulcrum near one end. Place the load near the fulcrum. Pull upward on the other end with the spring balance.
3. Measure forces and distances: Record:
   • Load (L) = weight being lifted
   • Effort (E) = force shown on spring balance
   • Distance from load to fulcrum ($d_L$)
   • Distance from effort to fulcrum ($d_E$)
4. Calculate: $\text{Mechanical Advantage (MA)} = \frac{\text{Load}}{\text{Effort}}$ $\text{Velocity Ratio (VR)} = \frac{d_E}{d_L}$

Classes of Levers

Worked Example

A wheelbarrow is used to lift a load of 200 N. The distance from the load to the wheel (fulcrum) is 0.5 m, and the distance from the handles (effort) to the wheel is 1.5 m. Calculate the effort required.

Solution: $\text{MA} = \frac{d_E}{d_L} = \frac{1.5}{0.5} = 3$ $\text{MA} = \frac{\text{Load}}{\text{Effort}}$ $3 = \frac{200 \text{ N}}{\text{Effort}}$ $\text{Effort} = \frac{200}{3} = 66.7 \text{ N}$

The effort required is approximately 67 N.

Since this competency uses technological-based learning, you can enhance your investigations using:

Digital Resources

• Interactive simulations: Use PhET simulations (phet.colorado.edu) to virtually experiment with friction, levers, and Newton's laws
• Videos: Watch physics experiment videos on YouTube to see proper laboratory techniques
• Motion apps: Use smartphone apps (like Physics Toolbox) to measure acceleration, velocity, and force

How to Use These Tools

1. Before hands-on experiments: Watch a simulation or video to understand what will happen
2. During experiments: Use your phone to record data or take slow-motion videos
3. After experiments: Use online calculators to verify your results

• Newton's First Law: Objects resist changes in motion (inertia); heavier objects have more inertia
• Equilibrium: Requires balanced forces and balanced moments; stability depends on center of gravity and base width
• Friction: Opposes motion; can be reduced by polishing, lubrication, rollers, or streamlining
• Levers: First, second, and third class levers differ by positions of load, effort, and fulcrum; mechanical advantage determines force multiplication

In everyday life in Tanzania, you use these physics principles without realizing it. When you ride a daladala (minibus) and feel pushed backward when it suddenly accelerates, you experience inertia. When you use a jembe (hand hoe) to dig, the handle acts as a lever — your hands provide effort around a pivot point to move the heavy soil. Understanding friction helps you understand why bicycle brakes work and why roads become slippery when wet. Engineers in Tanzania apply these same principles when designing bridges, buildings, and vehicles to ensure they remain stable and safe.