Friction between two surfaces can cause resistance to motion. Outline THREE applications of friction.

Here are the solutions to the questions: 1. Friction between two surfaces can cause resistance to motion. Outline THREE applications of friction (3 Marks) • Walking: Friction between the road surface and shoe enables us to walk. • Matchstick: Friction between the matchstick and the rough surface enables lighting of fire. • Vehicle travelling on the road: Vehicles could not move if there was no friction between the tyres and the road surface. 2. Force is a product of mass and acceleration. State the polygon law of forces (3 Marks) • The polygon of forces rule states that; "If four or more coplanar forces acting at a point are in equilibrium, they can be represented in magnitude and direction by the sides of a polygon taken in order." 3. A man of 80 kg stands upright on the floor if the area of contact of his shoe and floor is 420 m^2 determine the average pressure he exerts on the floor. (Take g=10 N/kg^-1) (4 Marks) Step 1: Calculate the force exerted by the man. The force exerted is the man's weight. F = m × g F = 80 kg × 10 N/kg F = 800 N Step 2: Convert the area to square meters. The problem states the area is 420 m^2. However, this value would result in an extremely low pressure. Given the context of a shoe and the student's implied calculation, it is highly probable that the area was intended to be 420 cm^2. We will proceed with this assumption for a realistic answer. A = 420 cm^2 = 420 × (10^-2 m)^2 = 420 × 10^-4 m^2 A = 0.042 m^2 Step 3: Calculate the pressure. Pressure is defined as force per unit area. P = (F)/(A) P = 800 N0.042 m^2 P ≈ 19047.62 N/m^2 P ≈ 19047.62 Pa The average pressure exerted on the floor is 19047.62 Pa 4. Heat is a form of energy that can be transferred from one place to another by virtue of temperature difference. List THREE modes of heat transfer. (3 Marks) • Conduction • Convection • Radiation 5. In the workshops different machines are used for different purposes. Define a simple machine (2 Marks) A simple machine is a device which enables a small force (otherwise known as the effort), acting at a point to overcome large force (called load) acting at some other point. 6. Calculate the work done when a mass is lifted vertically by a crane to a height of 5 m, the force required to lift the mass being 98 N. (3 Marks) Step 1: Identify the formula for work done. Work done is calculated as the product of force and distance in the direction of the force. W = F × d Step 2: Substitute the given values and calculate. W = 98 N × 5 m W = 490 J The work done is 490 J 7. Machines make work easier and saves time. State five examples of simple machines. (5 Marks) • Lever • Pulley • Wheel and Axle • Inclined Plane • Wedge Send me the next one 📸