SP15 Flashcards
describe the characteristic of an elastic object
when a force is removed off an object the object returns to its original shape
describe the characteristic of an inelastic objects
objects keep a new shape after force are removed
explain why bending stretching or compressing an elastic object needs two forces
- if one force is supplied then the object will just move in that forces direction
- such as a pole vaulter
- force from the weight of the person and the force of the floor on the pole causes the pole to bend
Describe the difference between elastic and inelastic distortion
elastic deformity
the object returns to its original shape after a force is removed ( elastic band)
inelastic deformity
the object doe not return to its original shape after the load is removed
( a string pulled too far)
Describe the difference between linear and non-linear relationships between force and extension
force exerted on spring = spring constant x extension
for a metal spring there is usually a linear relationship between the force and the extension, ( directly proportional)
however if the springs is stretched too far the relationship becomes non - linear
Explain why atmospheric pressure varies with height above the Earth’s surface
- atmospheric pressure is the total weight of air above a unit area at a certain altitude
- atmospheric pressure decreases with increasing height above the earth surface
- more elevation, less air molecules above so less weight so less atmospheric pressure
Describe the pressure in a fluid as being due to the fluid and atmospheric pressure
Pressure in a fluid is due to the depth of the fluid and atmospheric pressure.
the deeper you go the higher the pressure
Recall that the pressure in fluids causes a force normal to any surface
pressure in fluid causes a fore perpendicular to the surface of the object
Explain how pressure is related to force and area, using appropriate examples
pressure = force normal to a surface / area
Describe how pressure in fluids increases with depth
greater the depth an object is in fluid, the greater the pressure
- the fluid above the object, so greater weight so greater force felt, so greater pressure
Describe how pressure in fluids increases with density
the denser the fluid, the greater the pressure
- mass = density x volume
- the greater the density means greater weight of fluid on the object, so greater force and pressure
Explain why the pressure in liquids varies with density and depth
the pressure always depends on the weight of an object.
- by increasing the density of a fluid, it makes the same volume of water have greater weight so the pressure is greater.
( and vice versa) - by increasing the depth of the object in a fluid, there is more water above the object, so more weight on the object do a greater pressure
Explain why an object in a fluid is subject to an upwards force (upthrust)
( light weight abject like wood)
if the pressure exerted by an object is less than the fluid, the object will rise above the water to balance out the forces. ( so upthrust is equal to the weight of the block so it floats)
(heavy metal)
in heavy blocks they have high pressure, so it sinks in water, because they need a greater weight to balance them, so the water rise above the block so there is pressure above the block to balance the forces
what is up thrust equal to
up thrust is equal to the weight of fluid displaced
what is buoyancy
the upwards force that counteracts the weight
it is equal to the weight if fluid displaced by the object
