Chapter Gobbe & Pressure

Chapter GOBBE & PRESSURE, What is force? Force is a push or a pull that can change the shape of an object change the direction of motion Start or stop the motion SI unit of force: Newton (N) EXAMPLES: Pushing a door Pulling a drawer kicking a balوا Effects of force A force can Move a stationary object Stop a moving object Change the speed, direction, shape or size of an deject Contact & Non-contact forces. Contact force act only when objects touch. Muscular force A force that is applied by muscles. like lifting a bag. Frictional force: A force opposing motion. like brakes stopping the bicycle. Non-contact force act only without physical contact. Gravitational force force of attraction between Earth & objects. Magnetic force: forice exerted by magnets. →Electrostatic force force between charged objects Net force When more than one force acts on an object. If force act in same directions. they add up If force act in opposite directions they subtract. I only if forces are different If force is 0 object stays at rest or object moves wi constant speed. Pressure It is the force acting on a unit area. formula Pressure Force Area Force Area Pressure E SI unit of fance Pascal (Pa) Factors affecting PRESSURE, Pressure increases when area decreases ↑↓ Pressure decreases when area increases Simple! EXAMPLES : Sharp knife outs better than blunt knife, High-heel shoes exert more pressure than shoes. Pressure in liquids Pressure in liquid increases with depth. Water pressure is greater at the bottom of a tank. Atmospheric Pressure Air around us exerts pressure We do not feel it because it acts in all directions EXAMPLES:- Drinking with a strang suction cups sticking to walls Key TERMS TO RE-MEMBER [VERY EXAM FRIENDLY] force Pressure Friction Atmosphenc pressure Gravitational force. Do 000 Exercise: ① Which of the following best defines FORCE 2 A Energy stored in an object BA push/pull acting on an object The mass of an object The speed of an object Which of the following is a non-contact force? A) Frictional force Muscular force Gravitational force D Applied force ③ What's the SI unit of pressure? A Newton B) Joule Pascal D Watt