Force and Pressure Summary:
Force:
- 🔄 Definition: Push or pull.
- 🏋️♂️ Effects: Causes motion, stops, changes direction, speed, shape, and size.
- ⚖️ Unit: Newton (N).
- 1️⃣ Kilogram Force: Lifts 1 kg (~9.8 N).
- 🔄 Resultant Force: Single force like all combined forces.
- ⚖️ Balanced vs. Unbalanced Force.
Force Classification:
- 👥 Contact Forces: Muscular, Mechanical, Frictional.
- 🚫 Non-Contact Forces: Magnetic, Electrostatic, Gravitational.
Specific Non-Contact Forces:
- 💪 Muscular Force: Muscle action.
- 🛠️ Mechanical Force: Machine exertion.
- 🔄 Frictional Force: Opposes motion.
- 🧲 Magnetic Force: Attracts without touch.
- ⚡ Electrostatic Force: Charged object interaction.
- 🌍 Gravitational Force: Earth’s attraction.
Pressure:
- 💪 Factors: Force magnitude, applied area.
- 📏 Definition: Force per unit area (P = F/A).
- 📊 Unit: Pascal (Pa) or N/m².
Applications of Pressure:
- 🚛 Tyres on trucks.
- 🎿 Skis on snow.
- 🔪 Sharp knife blades.
- 🏠 Building foundations.
- 🎒 School bag straps.
- 🚜 Tank wheels.
- 🐪 Camel’s broad feet.
Pressure on Liquids:
- 💧 Liquids on container walls.
- 📏 Height-dependent pressure.
- 🔄 Sideways pressure: Lateral.
- 🌊 Equal at same depth.
- ⬇️ Increases with depth.
- 📏 Manometer measures.
Applications of Liquid Pressure:
- 🌊 Thicker dam walls.
- 🚰 Elevated water tanks.
Atmospheric Pressure:
- 🌐 Earth’s pressure.
- 📏 Barometer measures.
- 🏔️ Effect on Mountaineers: Nose bleeding at high altitudes.
Astronauts and Space Suit:
- 🚀 Space suit maintains pressure.
What is a Force??
Push or pull of an object is called as force.
What are the effects of Force?
Force can cause movement or motion or the object to move from rest.
- But when sufficient forces not applied the object does not move
Force can stop a moving object.
- Ex: applying brakes in the moving vehicle makes the objects to stop..
Force can change the direction of the motion of the moving object.
- Ex: tennis ball beaten by the players the force can cause the change in the direction of the object.
Force can change the speed of the moving object.
- Ex: Child playing in a swing. When you move the swing fastly the swing moves faster when less force is applied the swing moves lower.
Force can change the shape and size of an object.
- Example crushing the 🗞️ paper
- squeezing the toothpaste
- Kneading the flour
What is the unit of force??
- SI unit of force is Newton.
- It is denoted by N.
Define 1 kilogram force??
The force that is required to lift an object of mass 1 kg vertically upwards is called 1 kilogram force.
- 1 KgF = ~ 9.8 N
- I KgF = 1000gF
Define Resultant force??
- Resultant force is a single force that is applied to the object and would have same effect as all the separate forces acting upon it.
- Went to forces acts on an object in the same direction that resultant force is calculated by adding the forces. It moves the object in the direction of the applied force.
Difference between balanced and unbalanced force??
Balanced force | Unbalanced force |
Two equal forces act on an object in opposite direction. | Two unequal forces act on an object in opposite direction. |
Resultant force is zero | The resultant force is the difference between the two forces applied. |
Object does not move. | Object moves in the direction of the larger force. |
Ex: pushing a heavy box from both the ends applying the same force. | Ex: Tug of war |
How Force is classified??
Forces classified as
- Contact forces
- Non contact forces
Distinguish between Contact and Non contact force??
Contact force | Non contact force |
Contact force act only when the objects are in physical contact with each other and bring changes | Non contact forces are forces that can act even when the objects are not in physical contact with each other and bring changes. |
Types of contact forces are Muscular force Mechanical force Frictional force | Types of Non contact force Magnetic force Electrostatic force Gravitational force |
What is Muscular force??
- The force resulting due to the action of muscles is known as Muscular force.
- Ex: animals 🐘 elephant , bulls carry heavy loads and pull cart with the help of muscular force.
What is Mechanical force??
- The force exerted by the machine to do the work is called Mechanical force
- Ex: Sailboat use the wind energy to produce mechanical force that propels the boat.
What is Frictional force??
- It is also called as Force of Friction.
- The force acting along the two surfaces in contact which opposes the motion of one object over the other is called frictional force.
- Frictional force always opposes the motion of moving object.
- Force of friction or frictional force is due to the roughness of the surface of the object in contact
- When there is more roughness, more is the frictional force between them
- Ex: Moving ball stops after sometimes due to frictional force.
Why Magnetic force is an is a Non contact force??
- When magnet is brought near the iron object due to the magnetic force the iron object is attracted towards it
- Magnetic force is exerted even when the magnet and iron object or not in physical contact. So this is an example for non contact force
What is an Electrostatic force??
- The force exerted by a charged object on another charged or uncharged object is known as Electrostatic force.
- Ex: Rubbing a plastic comb in a dry hair several times and bringing it near the bits of paper.
- Electrostatic force acts here and attracts the paper towards the comb
Define Gravitational force??
- Force of attraction exerted by Earth on any object is called force of gravity or gravity.
- Ex: Throwing a ball or any object towards the space always brings it to down the earth.
- The force is due to the attraction of the object and that of the earth
Pressure
What are the two factors that depends on the applied force??
- Magnitude of the force applied
- Area over the force applied
Define Pressure??
- Pressure is a physical quantity that measures the effect of force per unit area.
- Pressure is a force acting on a unit area of the object.
- P = F /A
- The unit of pressure is Newton per square metre or Pascal ( N/m2 = Pa)
List some applications of pressure??
- Heavy trucks have more tyres
- Usually heavy truck have 6 to 14 tyres. These tyres increase the area of contact on which the weight acts and so it reduce the pressure on the ground.
- Skies have large area of contact so that it produces the pressure on the snow and enable the skier to slide over the snow without sinking in the snow.
- Cutting edge of knife blades axes are Sharp due to which the area of contact decreases and the pressure exerted by them increases.
- Large pressure helps to cut the objects easily.
- High raised building foundations are made wide so that they exert less pressure on the ground.
- School bags traps are made by so that when the child wears the school bag it produces less pressure on the shoulders.
- A Wide Steel belt is provided over the wheels of the army tank so that they exert less pressure on the ground.
- Broad feet of the camel enable set to walk easily on the sandy soil. this is because the broad feet exerts less pressure
Pressure on liquids
- Liquids exact pressure on the walls on the base of the container
- Pressure exerted by liquid on the walls of the container depends on the height of its column.
- Sideways pressure exerted by the walls of the container is called as lateral pressure.
- Liquids exerts equal pressure at the same depth
- The pressure of the liquid increases with the depth
- Manometer is a device used to measure the liquid pressure
List the applications of liquid pressure
- Walls of the dams are made thicker at the bottom than at the top.
- This is because thicker walls with stand greater pressure exerted by water at depth.
- In houses and buildings water tanks are placed at high heights. This is because when the height is greater the pressure of the water will be more and it reaches the tap of the houses at the greatest speed.
Define Atmospheric pressure??
- Layer of the air surrounding our earth is called atmosphere.
- The pressure exerted by the air is due to its own weight is known as atmospheric pressure.
- It is measured using an instrument called Barometer.
- There are two types of barometer
- Mercury barometer or Fortin’s barometer
- Aneroid barometer
What happens to mountaineer when they reach high altitudes??
- In high altitudes the atmospheric pressure decreases.
- Mountaineers suffer from nose bleeding and this is because at high altitudes atmospheric pressure decreases that is much lesser than our blood pressure.
- This is because some of the blood capillaries burst and result in bleeding.
Why astronauts wear special space suit??
- Since that is no atmosphere outside the earth astronauts wears a space suit.
- This helps them to maintain normal atmospheric pressure.
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