Topic 5b- forces and their effects

how would u change the shape of an object

More than one force needs to be acting on it

What does it mean if an object is elastically deformed

It can go back to its original shape and length after the force has been removed

What does it mean if an object is inelastically deformed

It doesn’t return to its original shape and length after the force has been removed

What are elastic objects

Objects which can be elastically deformed

What is extension

The increase in length of a spring when it’s stretched

Force and extension equation

Force (N) = spring constant (N/m) x extension (m)

What does spring constant depend on

The material being stretched- a stiffer spring has a greater spring constant

What is limit of proportionality

The limit to the amount of force you can apply to an object for the extension to continue increasing proportionally

What is Hooke’s law

That force and extension are directly proportional

Elastic potential energy calculation

Ee = ½ x k x e²

What is elastic potential energy

The energy transferred to an object as it’s stretched

How to find energy stored in elastic potential energy store with a graph

By calculating the area under the linear force-extension graph up to that force

What is a moment

the rotational or turning effect of a force

What is the equation to find moments

m = Fd

What does the amount of force needed to produce a particular moment depend on

The perpendicular distance the force is applied

What is a levers effect on moments

Levers reduce the amount of force needed to get the same moment by increasing the distance from the pivot at which the force is applied

What are gears used for

Used to transmit the rotational effect of a force from one place to another

Explain why a larger gear will turn slower than a smaller gear

The force transmitted to a larger gear will cause a bigger moment as the distance from the edge to the pivot is greater

How does fluid pressure work

Particles have a mass so when particles in a fluid collide with a surface they exert a force on it as pressure is force per unit area a pressure is exerted on the surface by the fluid

How does the force due to the pressure of a fluid acts to a surface

Normal (at right angles)

What is the equation for pressure at the surface of a fluid

Pressure = force/ area

What is density of a liquid affect on pressure (weight)

The denser the liquid the larger its mass per unit volume and so larger the weight

What is density of a liquid affect on pressure (particles)

The denser the liquid the more particles there are in a given volumes so more particles are able to collide causing more collisions leading to a higher force exerted and so higher pressure

What is upthrust

The resultant force acting upwards on a submerged object due to the large pressure at the bottom of the object than the top

What is upthrust equal to

The weight of the fluid that has been displaced by object

Does the object float or sink if the upthrust is larger than the objects weight

Floats

What will happen to an object if it’s more dense than the liquid it’s in

It will sink

Explain what happens to fluid pressure as depth increases

The number of particles above the point increases and the weight of these particles adds to the pressure experienced at that point

What is the equation for pressure at a certain depth

Pressure = height or depth x density x gravitational field strength

What is atmospheric pressure

Pressure created on a surface by air molecules colliding with the surface

Why does atmospheric pressure decrease as altitude increase

•As altitude increases the atmosphere gets less dense this means fewer air molecules are able to collide with the surface therefore less atmospheric pressure

•fewer air molecules above a surface this means weight of the air molecules above which contributes to atmospheric pressure decreases