Studied by 11 peopleHow is length measured?
Using a ruler
Unit of length?
Meters, m
How can you find volume of regular solid
By calculation
Use ruler to approximate measurements
Then the appropriate formula
How can you find volume of an irregular solid
By submersion
Fill measuring cylinder with water and read initial volume
Submerge the object and measure final volume
The change of volume = volume of object
How can time be measured
Clocks or stopwatches
How can measurement accuracy increase?
By taking multiple readings and finding average
How can very small distances be measured?
Micrometre screw guage
What’s an analogue device?
A measuring device requiring user to read from a scale to obtain measurements
What’s a digital device?
Measuring device that shows the measurements on a display rather than requiring user to read from a scale
Distance
measure of how far an object moves, no direction thus scalar
What’s a pendulum?
It is a weight suspended from a pivot so that it can swing freely
What is volume?
Amount of space an object takes up
What are the 3 main components of motion?
Speed, direction, acceleration
Average acceleration formula?
v=m/s d=m t=s
What is the difference between speed and velocity
Speed is scalar, no direction
Velocity is vector, with direction
Average acceleration (m/s2
Vf-Vi (m/s)/time(s)
What is gradient of displacement-time graph?
Velocity
What does curved line represent in DT graph?
Acceleration/deceleration
What does the gradient of velocity-time graph represent?
Acceleration at that point
What does the area under of velocity-time graph represent?
Displacment
What does a curved line in velocity-time graph represent?
Changing acceleration
What does speed-time graph look like when object is at rest?
y axis=0
What does speed-time graph look like when object moves at constant speed?
A flat line (0 gradient)
What does speed-time graph look like when object is moving with a changing speed?
A non-zero gradient
Explain how terminal velocity is reached?
TV is when resistance force = acceleration
What is deceleration?
Negative acceleration (slowing down, decreasing speed)
What is air resistance?
The resistance of an object traveling through air
What is free fall?
Motion under the force of gravity alone
What is linear motion?
Motion for which acceleration is not constant
What is gravitational field?
A region where a mass will experience non-contact gravitational force
How does mass increase with gravitational field?
Increase in mass = increase in gravitational field
How is a proportional relationship drawn?
Straight line through origin
What is the relationship if its a straight line NOT through origin?
Linear relationship
Define mass?
Amount of matter in an object and a measure of its resistance to acceleration/motion
Define weight?
The force acting on an object due the effect of its mass and gravity
State the conversion of 1 kg to g
1kg = 1000 grams
Weight formula?
Weight (N) = mass (kg) * g (N/kg)
What does “g” represent?
Gravitational field strength
How can weight (and masses) be measured/compared?
A force meter (spring balance)
A weighing scale, which measures its weight and converts it into mass (by dividing by g)
Mass vs weight of same object on 2 different planets:
The mass is the same
Weight is different due to different gravitational field strength (g)
State the formula for density
density (kg/m³) = mass (kg) / volume (m³)
density is also shown as rho “p”
Describe a method to find density of regular solid
Take measurements of relative dimensions with a ruler
Calculate volume with appropriate formula
Measure the mass with using a balance and density with formula p=m/v
Describe a method to find density of an irregular solid
Measure volume by submersion (read V of L, drop object, then read final V, the change is V of object)
Measure mass with balance
Use density formula
Describe a method to find density of a liquid
Place an empty beaker on top of a balance and zero the device
Pour liquid into beaker to determine mass
Pour the same L into a measuring cylinder and read off the volume
Use density formula
When do objects float in water?
When object is less dense than the water (displaced by it)
When upthrust is = or > than objects weight
When do objects sink in water?
When the density of the object is greater than the water
When upthrust is < than objects weight
When does a liquid float?
L of lower density will float on L of higher density
Define resultant force
Sum of all forces acting on an object (after taking into consideration calculation and the direction)
What happens if RF acts on an object?
Causes a momentum change in the force’s direction
How can the RF can the motion of an object?
Speed
Direction
How can RF be found?
Adding force vectors together, tip (arrow) to tail
What happens if zero RF?
Object remains stationary
Or continues in same direction with same speed
Define friction
Opposes motion between 2 forces acting on/sliding past each other
Give an example of frictional force
Air resistance
What does friction result in when work is overdone?
Heating
When does circular motion occur?
When force is acting perpendicular to motion of an object
Describe speed and velocity of an object in circular motion
Speed is constant
Velocity is always changing due to changing direction
Give an example of a force causing circular motion
Gravity, causing orbit
State Hooke’s law
The force on an object (spring, wire) directly prop to its extension
Hooke’s law formula?
F (N) = k (N/m) * x (or e, m)
When does Hooke’s law not apply?
When elastic limit is reached (limit of proportionality)
How does limit of proportionality look on a graph
Graph stops being linear
What is a moment?
Rotational/turning effect of a force
Moment formula?
note; distance is the perpendicular distance from the force to pivot
When does rotational equilibrium occur?
Sum of CW moments = sum of ACW moments
Also called principle of moment
When is equilibrium reached?
When no RF or turning effect (cw = acw moments)
What is a centre of mass?
A single point through which the force of the an objects weight acts
How to find centre of mass of a lamina?
Suspend object and plumb line from same point
Trace plump line thread with a pencil
Repeat with diff points
Centre of mass is where all lines cross
What is vector?
Both mag and direction
What is scalar?
Only mag
Vector examples?
Scalar examples?
How can RF be shown visually?
Momentum formula?
Time taken for the change of momentum to occur is prop to?
RF felt by object
(newtons 2nd law, F=ma)
Formula with RF and mom.?
What is impulse?
Change of mom. in an object caused by force acting on it for a period of time
What is principle of conservation of mom.?
Mom. is always conserved in explosion/collision, so no net change in mom.
Mom. before = Mom. after (if no external forces)
What type of energy is stored in moving object?
Kinetic (Ke)
In terms of energy what happens when you list an object?
the GPE increases
Ke formula?
GPE formula?
What happens when work is done against friction/resis
Less change of Ke bc some energy is lost through heating
What forms of energy don’t come from sun?
Geothermal
Nuclear
Tidal
What is source of sun’s energy
Nuclear fusion
What are main energy resources available?
Renewable energy def?
Not finite
Non-renewable energy?
Fossil fuels
Nuclear fuel
Renewable energy?
Why is NR energy used more?
Larger energy output per kg of fuel
What is efficiency?
ratio of useful work done to energy supplied, given as %
Efficiency formula?
How to increase efficiency?
Reducing waste output
Recycling waste output
Define work done
Work done on an object is when energy is transferred, = to product of force and distance
Work done formula?
Define power
Rate at which energy is transferred
Power formula?
Pressure formula?
How dies depth affect pressure?
Pressure increases with depth, bc of gravitational force of the fluid above
Pressure at diff points formula?
Note
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