C. Answer the following in one word.
1. Push or pull acting on a body:
force
2. Turning effect of force:
3. The normal force acting per unit area:
Pressure exerted by gases:
5. Liquid pressure exerted on the walls of a container in which it is stored:
Answers
Answer:
Explanation:
1Chapter 3 Force and Pressure Chapter Objectives In this chapter, you will learn about: Turning effect of force (moment of force): concept, definition and calculation Pressure Definition Unit Calculation of pressure in simple cases Pressure exerted by liquids (Qualitative only) Pressure exerted by gases- Atmospheric pressure (Qualitative only) Did you know that the atmospheric pressure of the earth is so much that it can crush the human body easily? But it does not; can you guess why? INTRODUCTION In the earlier classes we learnt about the concepts of Force and Pressure. Before proceeding to study more about them, it is important that we revise a little of what we learnt about them. Firstly, Force is defined as a pull or push on a body that alters its state of rest (causing it to move), of motion (causing it to come to rest), the direction of its motion, its speed, its shape or its size. The types of forces are: Contact Forces—Collision Forces, Muscular Forces, Normal Forces, Tension, Mechanical Forces and Friction; and non-Contact Forces— Gravitational, Magnetic and Electrostatic. Secondly, Pressure has been defined as the magnitude of force acting upon a surface per unit area. So pressure is dependent upon the amount of force applied and the area of the surface in touch. TURNING EFFECT OF FORCE In simple language, the 'turning effect of a force' is the ability of a force applied to make something turn around a fixed point or pivot. The 'turning effect of a force' is also known as the Moment of a Force or Torque (T) and is defined as the product of a force and the perpendicular distance from the line of action of the force to the pivot or point where the object will turn. It is calculated in Newton-metres (Nm). Nm is a vector quantity. Thus, Moment of a Force = Force >< Perpendicular Distance from the Force to the pivot = Newton >< metres = Newton-metres The Moment of a Force can be explained with the help of the simple experiment such as a door opening around a hinge that is fixed to a wall or a frame or a screw moving forward while turning around a nut. Nut 15 cm Spanner 10 N Fig. 3.1 Turning Effect of a Force Moments can be both Clockwise as well as Counter- clockwise. In the state of equilibrium, the sum of the total clockwise moments always equals the total counter-clockwise moments. This is known as the Principle of Moments. For example, if the sum of clockwise forces is fl and their distance from the pivot is . Teaching Tip: The children should be made conceptually clear about what pressure is and what its effects are.