SECTION A: (40 MARKS) Attempt ALL questions in this section 1. A force exerted on a body can cause a change in either the shape or the motion of the body. State FOUR effects of force on a body.

The force $F = 1000$ N.  
Pressure $P = \frac{F}{A}$.
$$
P = \frac{1000\, \text{N}}{0.0025\pi\, \text{m}^2} = \frac{400000}{\pi}\, \text{Pa}
$$
$$
P \approx \frac{400000}{3.14159}\, \text{Pa} \approx 127323.95\, \text{Pa}
$$
The pressure on the piston is $\boxed{\text{127324 Pa}}$.

5. Step 1: Convert the velocity from km/h to m/s. $v = 72\, \frac{\text{km}}{\text{h}} \times \frac{1000\, \text{m}}{1\, \text{km}} \times \frac{1\, \text{h}}{3600\, \text{s}}$ $v = \frac{72 \times 1000}{3600}\, \frac{\text{m}}{\text{s}} = 20\, \frac{\text{m}}{\text{s}}$

The force resisting motion $F = 800$ N.  
Since the lorry is moving at a constant velocity, the attractive force must be equal to the resisting force.  
Power $P = F \times v$.
$$
P = 800\, \text{N} \times 20\, \frac{\text{m}}{\text{s}} = 16000\, \text{W}
$$
The attractive power necessary is $\boxed{\text{16000 W}}$.

6. Five factors to consider when selecting engineering materials for high-temperature operation are: * High melting point: The material must remain solid and stable at the operating temperature. * Creep resistance: Ability to resist permanent deformation under prolonged stress at high temperatures. * Oxidation/Corrosion resistance: Resistance to chemical degradation when exposed to high temperatures and reactive environments. * Thermal expansion coefficient: A low coefficient is desirable to minimize dimensional changes and thermal stresses. * High-temperature strength: The material must retain sufficient mechanical strength and hardness at elevated temperatures.

7. i. Density: The mass per unit volume of a substance. It is calculated as $\rho = \frac{m}{V}$, where $m$ is mass and $V$ is volume. ii. Relative density: The ratio of the density of a substance to the density of a reference substance. For liquids and solids, the reference substance is usually water at $4^\circ\text{C}$. It is a dimensionless quantity.

8. Quantities in engineering and science are divided into scalar and vector quantities.

   • Scalar quantities have only magnitude. Examples include mass, temperature, distance, speed, and energy.
   • Vector quantities have both magnitude and direction. Examples include force, velocity, displacement, acceleration, and momentum.

9. i. Mechanical energy into electrical energy: Generator or Dynamo. ii. Heat energy into electrical energy: Thermoelectric generator or Thermocouple. iii. Chemical energy into electrical energy: Battery or Fuel cell. iv. Electrical energy into light energy: Light bulb (e.g., incandescent, LED) or Fluorescent lamp.

10. i. Stable equilibrium: An object is in stable equilibrium if, when slightly displaced from its equilibrium position, it tends to return to that position. This occurs when the center of gravity is at its lowest possible point.

    Sketch for stable equilibrium:
    A cone resting on its base. If you tilt it slightly, it will return to its original position.

          /\
         /  \
        /____\
        ------
    

    Copy

    (Imagine a cone standing upright on its wide base. If pushed slightly, it wobbles and settles back.)