Answer Briefly: 1. What is friction? What are the two important properties of friction? 2. What causes friction? 3. Why are spaceships provided with heat shields?
Hint: To answer the above question, we need to know what friction is. Friction is a force that acts between two surfaces that works to prevent motion between them. This process produces energy in the form of heat and can cause wear and tear of surfaces.
Complete step by step answer: 1. Friction is the force exerted by two surfaces sliding (or attempting to slide) over one another. When you try to drive a book across the concrete, for example, friction makes it difficult. Friction often acts in the opposite direction from where the object is going or attempting to move. A moving object is often slowed by friction. The amount of friction is determined by the materials used to construct the two surfaces. Friction is increased as the surface becomes rougher. Friction generates heat as well. You can feel your hands getting warmer if you rub them together quickly. 2. Cause of friction: Friction is a force that prevents two objects or materials from moving in the same direction. Molecular adhesion, surface roughness, and deformations are the sources of this resistive force. When two materials are brought into close proximity, adhesion is the molecular force that results. 3. Heat shields are used to secure spaceships during their journey through and reentry into the earth's atmosphere. The ship would explode if they didn't have these shields.
Note: We all want to reduce friction from time to time. We use oil, for example, to minimize friction between moving parts within a car engine. The oil separates the surfaces and allows fluid to flow between them. Since there is less friction, the car's moving parts wear less and emit less heat.