What kind of quantity is force
Force is a vector quantity, as both direction and magnitude are important
| Term | Definition |
|---|---|
What kind of quantity is force | Force is a vector quantity, as both direction and magnitude are important |
what can be used to measure force | spring balance can be used |
SI unit | newton [N] |
other units | kg m/s^2 and kgf |
1 kg m/s^2 = | 1 N |
1 kgf | 9.8 N |
1 gram force is | the force required to move a body of mass 1 g towards itself or the force required to lift a body of mass 1 g vertically upward |
1 kgf is | The amount of force required to move a body of mass 1 kg towards itself or in the vertically upward direction. |
1 dyne [CGS unit of force] | 10^-5 N |
what happens if a body is fixed on a pivot at force is applied to it | the body will turn on its pivot |
moment of force | it is the product of the magnitude of force and perpendicular distance between the pivotal point and the point of application of force |
other name for moment of force | torque |
moment of force = | force*perpendicular distance |
SI unit | newton meter [Nm] |
1 kgfm = | 9.8 Nm |
CGS unit | dyne cm |
1 dyne cm = | 10^-5 N * 10^-2 cm
= 10^-7 Nm |
pressure | the normal force [thrust] acting on the unit area of a surface. |
formula for pressure | Force [thrust]
----------------------
Area |
SI unit for pressure | Pascal |
other units | Kilopascal, N/ m^2 |
how is pain in ears caused by diving to the bottom of a pool an example of pressure | this is because the water has most pressure at the bottom, and all the water in the pool is pressing down on the person, causing the air in their ears to squeeze to a smaller volume, increasing the pressure. |
how is the long length of handbag handles an example of pressure | The handles increase the total contact area, reducing the strain on our hands and shoulders. |
Why do thumb tacks, nails, and awl pins have flat heads and pointed tips? | This is because when they are hit on the head, they are pushed down, because the tips have a very small surface area, increasing the pressure. |
why do porters place a round piece of cloth on their heads when carrying heavy loads on it? | The cloth increases the area of contact, so the overall pressure on the head is reduced, making it easier to carry. |
why are sledges used in snowy areas | They are used because their high surface area allows them to exert less pressure on the snow, allowing them to slide on the snow. |
why do heavy duty trucks have more tires than normal vehicles? | They have more tyres to support the truck's immense weight, and the wider tyres reduce pressure on the road. |
thrust | a force acting perpendicular to the body. |
how much thrust is exerted by a body when placed on the ground | the thrust is equivalent to its own weight |
lateral pressure | the force exerted by a liquid on the walls of its container |
factors affecting liquid pressure | 1. height of the liquid column above the point [depth]
2. density of the liquid |
manometer | it is a device used to measure the pressure exerted by a liquid. |
manometer structure | It consists of a U-shaped tube with either mercury or water. One end is connected to a thistle funnel which has a rubber membrane stretched over its mouth, and the other end is open to air. |
how does it show pressure | After placing the thistle funnel in the liquid, the level of the liquid in the manometer should change. To measure the pressure of a liquid, check and note down the level of the liquid before conducting the experiment, then note down the level of water/ mercury in the tube. The difference between these 2 values will be the pressure exerted by the liquid on the rubber membrane of the funnel. |
How can you prove that a liquid seeks its own level | Take a glass pipe with any number of tubes of different shapes and sizes, along with some water. Fill the water into one of the pipes with water and observe the movement of water in all the pipes. The water level in all tubes should be the same irrespective of the shape or size of the tube. |
hydrostatic paradox | It states that the pressure exerted by a liquid column depends only on its height, not on the container's shape or size. |
Why are the walls of dams built thicker at the bottom | Because of the lateral pressure exerted by the water, the dams need to be built thicker at the bottom, where more pressure is exerted. |
why do deep sea divers have special suits | because our bodies can't withstand the magnitude of pressure at that depth |
what is gas pressure | The pressure exerted by a gas on the walls of its containing vessel. It is caused by the force exerted by molecules striking the walls. |
what is atmospheric pressure | the pressure exerted by the atmosphere on a unit area of the earth. it increases with altitude and decreases with depth. |
what is the atmospheric pressure at sea level | 101.3 kilopascals or approximately 100 kpa. |
why do we not feel the effect of atmospheric pressure | because the blood in our body exerts lightly more pressure internally. |
how can we drink through a straw | when the air from a straw is removed, the pressure drops and the atmospheric pressure pulls the liquid upwards |
how do suction cups work | When the cup is pressed against a wall, the air between the wall and the cup is removed, creating a vacuum. This reduces the pressure, and the atmospheric pressure acts inwards and presses the suction cup, keeping it in place. |
how do syringes work | When the piston is pulled out, there is more available space, and this means the pressure inside the syringe is less than the atmospheric pressure, so the liquid is forced into the syringe. |
why do noses bleed at high altitudes | when we are at a high altitude, the atmospheric pressure decreases, but the pressure exerted by our blood stays same. because of this change in pressure, our noses bleed. |
movement of liquids with reference to atmospheric pressure | liquids move from high to low pressure. |