Science end of years revision

what is a force?

A push or pull that can cause an object to change shape, change direction and change speed

what is the unit of measuring force?

Newtons (N)

how do you represent a force?

an arrow

what equipment can be used to measure force?

Newton meter

contact forces:

tension, air resistance, friction

non contact forces:

magnetism, gravity, electrostatic

friction and air/water resistance

contact forces that are only present if two objects are in contact with eachother

what is generated when an object is moving through a liquid or gas

a drag force

what can you use to reduce friction between two objects?

a lubricant

what does a lubricant do?

makes surfaces smoother

what can we do to reduce the air or water resistance acting on an object?

make the object streamlined

what is the resultant force in balanced forces

0

what will the resultant force have on in unbalanced forces

a positive result force

what happens when we squash a ball?

is changes shape- it becomes deformes (compressed)

how is a reaction force created?

by working against the force that is stretching the elastic band

what is it called when you stretch an amount?

the extension

what happens if you apply a force too great to a spring?

the spring will stretch too far and will not go back to its original length. this is called the elastic limit

what happens when you double the force applied to a spring

the extension will also double

hooke’s law

“If the extension doubles when you double the force then the object obeys Hooke’s Law.”

independant variable

a variable that you change e.g force applied

dependant variable

a variable that you measure

control variable

a variable that you control e.g same spring

method for hooke’s law practical

1. set up the apparatus

2. add a 10g mass to the holder and record the length

3. add another 10g mass and record the new length

4. take away the previous spring length from the new length to calculate the extention

what is the point where hooke’s law doesn’t apply

the limit of proportionality

hooke’s law equation

force (F) = spring constant (k) x extension (e)

units for force, spring constant and extension

force- N spring constant- N/m

properties of metals

high melting and boiling points, strong, malleable (bends easily), good conductors of heat and electricity, ductile (can easily be drawn into wires

properties of non metals

low melting and boiling points, good insulators, brittle

the alkali metal react with oxygen to form what?

a metal oxide

what is group one called in the periodic table?

alkali metals

elements found in group 7

fluorine, chlorine, bromine, iodine, astatine

what could we do to reduce the risks of using halogens?

wearing goggles and lab coat, using a fume cupboard to remove the toxic gases produced by halogens