Force and Pressure 1 1 What are Forces

Force and Pressure 1 1

What are Forces? n A push or pull 2

Examples of Forces Squeezing n Stretching n Twisting n Folding n 3

Effects of Forces Object’s shape changes n Object’s size changes n Stationary object moves n 4

Effects of Forces Moving object stops n Moving object speeds up or slows down n Direction of an object’s motion changes n 5

Weighing scale 6

Tsunami 7

Weight lifting 8

Ultimate frisbee 9

Naruto vs Sasuke 10

Measuring Forces S. I unit of force is newton (N) n Spring balance used to measure the amount of force applied n 11

Types of Spring Balance Extension spring balance n Spring stretches when a pulling force acts on it n Greater force, greater extension n Spring attached to a pointer which indicates the amount of force exerted on the spring n 12

Types of Spring Balance Compression spring balance n Spring compressed when a pushing force acts on it n Greater force, greater compression n Spring attached to a pointer which indicates the amount of force exerted on the spring n 13

Forces Around Us Gravity n Friction n Magnetism n 14

Gravity is the force that attracts objects to the Earth n Mass is a measure of the amount of matter in a body n Weight is a measure of the gravitational force exerted on the object n 15

Frictional force acts when one materials rubs against another n Friction is useful in walking and when applying brakes to stop a car n Constant friction leads to wear and tear n Friction produces heat n 16

Magnetism is the force exerted by a magnet on magnetic materials such as iron and steel n Every magnet has a North pole and a South pole n Like poles repel n Unlike poles attract n 17

What is Pressure? Amount of force acting on a unit area n A sharp object pierces a surface more easily than a blunt object n 18

Calculating Pressure = Force Area 19

Applications of Pressure in Everyday Life Bulldozer n Can openers n Knife n Plane n Suction cups n 20