Force & Pressure 💥

Force - The push or pull of an object

• Forces develop due to an interaction between 2 bodies

• SI Unit of time = Newton (N)

• 1N = 10_⁵ Dyne

Effects of Force -

• Changes Speed

• Changes Direction

• Changes Shape

  If the net force on an object is 0, the first 2 are not possible, but even if the net force is 0, the shape can be changed

Types of force -

1. Contact Force : Where contact is required to apply force, without contact, it can’t be applied

   • Muscular Force

   • Frictional Force

2. Non - Contact Force : The force which can be applied without contact. It doesn’t require contact to act

   • Gravitational Force

   • Magnetic Force

   • Electro static Force

Net Force - The total amount of force applied on an object

• If force is in the same direction, it gets added

• If force is in opposite directions, it gets subtracted

Balanced Force : When the same amount of force is applied on an object from Opposite directions and the net force is 0

Unbalanced Force : More force is applied on one direction, so the movement happens in one direction

Thrust - Force acting perpendicular to a surface

• It has the same properties of force

• Vector quantity ( has scale & direction)

Pressure = The thrust acting per unit area

• No direction

• Scalar quantity ( A physical quantity that can be described by its magnitude/ size and doesn’t require direction)

• F/A or Thrust/Area

• ^ Area = less Pressure

• Less area = ^ Pressure

Liquid Pressure :

• Pressure is exerted on the walls of the container

• Pressure is equal at same depth

• Pressure increases with depth

• Pressure is exerted in all directions

• Higher density of liquid = higher pressure (at the same depth)

• The pressure is same at the same height if the liquids are the same

Atmospheric Pressure : The weight of the air exerts a thrust pressure on the Earth’s surface, the thrust exerted on a unit area of the Earth’s surface is atmospheric pressure

• Higher altitude = Lower atmospheric pressure

• Straw

  • When we suck something from a straw, we suck the air, decreasing the pressure in the straw

  • So, the atmospheric pressure outside pushes the liquid into the straw

• Rubber sucker

  • When it’s pressed on a surface, it expels the air in it

  • So, inside low pressure & outside high pressure, jo pushes the sucker onto the wall

• Syringe, when the plunger is pulled

  • When the plunger is pulled, more vacuum space is created, so it’s low pressure

  • So, outside ka high pressure will push the liquid into the syringe

Why is it easier for a camel to move in sand than a horse?

Bcoz, a camel’s foot is larger, so pressure per unit area is lesser and the camel doesn’t sink into the sand

A horse’s foot is small, so the pressure applied per unit area is more, which will cause the horse to sink