AS & A Level Physics 9702 REVISION NOTES
11.2 Temperature scales a) understand that a physical property that varies with temperature may be used for the measurement of temperature and state examples of such properties
A physical property that varies with temperature may be used for the measurement of temperature e.g. o Change in volume of a liquid or gas o Change in pressure of a gas o Change in electrical resistance o Change in e.m.f. of a thermocouple Physical property should have the following qualities: o Change in property with temp. should be large enough to be measured accurately o Value of temperature recorded should be reproducible i.e. m.p. should be the same when measured a 2nd time
12.2 Internal energy and the first law of thermodynamics b) relate a rise in temperature of a body to an increase in its internal energy
A rise in temperature of a body is an increase in its internal energy
11.2 Temperature scales b) understand that there is an absolute scale of temperature that does not depend on the property of any particular substance (i.e. the thermodynamic scale and the concept of absolute zero)
Absolute zero: temperature at which a system has minimum internal energy (not zero) - impossible to remove any more energy - at 0 Kelvin
9.1 Stress and strain b) describe the behaviour of springs in terms of load, extension, elastic limit, Hooke's law and the spring constant (i.e. force per unit extension)
According to Hooke's law, the extension produced is proportional to the applied force (due to the load) as long as the elastic limit is not exceeded. 𝐹 = 𝑘𝑒 Where 𝑘 is the spring constant; force per unit extension
7.1 Kinematics of uniform circular motion b) understand and use the concept of angular speed to solve problems
Angular velocity: the rate of change of the angular position of an object as it moves along a curved path W = 0/t 0=angle in degress
5.1 Types of force d) understand that the weight of a body may be taken as acting at a single point known as its centre of gravity
Centre of gravity: point through which the entire weight of the object may be considered to act
7.2 Centripetal acceleration and centripetal force c) recall and use centripetal force equations F = mr~2 and F r mv2
Centripetal force: resultant force acting on an object moving in a circle, always directed towards the center of the circle perpendicular to the velocity of the object F = mv^2/r or mrw^2
5.3 Equilibrium of forces b) understand that, when there is no resultant force and no resultant torque, a system is in equilibrium c) use a vector triangle to represent coplanar forces in equilibrium
Conditions for Equilibrium: o Resultant force acting on it in any direction equals zero o Resultant torque about any point is zero.
5.2 Turning effects of forces b) understand that a couple is a pair of forces that tends to produce rotation only
Couple: a pair of forces which produce rotation only To form a couple: o Equal in magnitude o Parallel but in opposite directions o Separated by a distance 𝑑
13.1 Simple harmonic oscillations c) understand and use the terms amplitude, period, frequency, angular frequency and phase difference and express the period in terms of both frequency and angular frequency
Displacement(X): instantaneous distance of the moving object from its mean position Amplitude (A): maximum displacement from the mean position Period (T): time taken for one complete oscillation Frequency (F): number of oscillations per unit time Angular frequency (W): rate of change of angular displacement W = 2pieF Phase difference #$: measure of how much one wave is out of step with another wave 0 = 2piet/T where T is time period and t is time lag between waves
6.2 Work and efficiency c) recall and understand that the efficiency of a system is the ratio of useful energy output from the system to the total energy input
Efficiency: ratio of (useful) output energy of a machine to the input energy 𝐸𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦 = 𝑈𝑠𝑒𝑓𝑢𝑙 𝐸𝑛𝑒𝑟𝑔𝑦 𝑂𝑢𝑝𝑢𝑡/ 𝑇𝑜𝑡𝑎𝑙 𝐸𝑛𝑒𝑟𝑔𝑦 𝐼𝑛𝑝𝑢𝑡 × 100
9.2 Elastic and plastic behaviour a) distinguish between elastic and plastic deformation of a material
Elastic deformation: when deforming forces removed, spring returns back to original length Plastic deformation: when deforming forces removed, spring does not return back to original length
6.3 Potential energy and kinetic energy d) understand and use the relationship between force and potential energy in a uniform field to solve problems
Electric potential energy: arises in a system of charges where there are either attractive or repulsive electric forces between them.
12.2 Internal energy and the first law of thermodynamics c) recall and use the first law of thermodynamics DU = q + w expressed in terms of the increase in internal energy, the heating of the system (energy transferred to the system by heating) and the work done on the system
First law of thermodynamics: the increase in internal energy of a system is equal to the sum of heat supplied to the system and the work done on the system ΔU = q + w o ΔU: increase in internal energy of the system o Q: heat supplied to the system o W: work done on the system
8.2 Gravitational force between point masses a) understand that, for a point outside a uniform sphere, the mass of the sphere may be considered to be ...
For an isolated point mass, the gravitational field is spherical in shape with the mass at the center
5.1 Types of force a) describe the force on a mass in a uniform gravitational field and on a charge in a uniform electric field
Forces on charge in electric fields: a region of space where a charge experiences an (attractive or repulsive) force due to the presence of another charge.
5.1 Types of force c) show a qualitative understanding of frictional forces and viscous forces including air resistance (no treatment of the coefficients of friction and viscosity is required)
Frictional force: force that arises when two surfaces rub o Always opposes relative or attempted motion o Always acts along a surface o Value varies up to a maximum value Viscous forces: o A force that opposes the motion of an object in a fluid; o Only exists when there is motion. o Its magnitude increases with the speed of the object
6.3 Potential energy and kinetic energy c) distinguish between gravitational potential energy and elastic potential energy
Gravitational Potential Energy: arises in a system of masses where there are attractive gravitational forces between them. The g.p.e of an object is the energy it possesses by virtue of its position in a gravitational field. Elastic potential energy: this arises in a system of atoms where there are either attractive or repulsive shortrange inter-atomic forces between them.
8.1 Gravitational field a) understand the concept of a gravitational field as an example of a field of force and define gravitational field strength as force per unit mass
Gravitational field an example of a field of force Gravitational field strength: gravitational force per unit mass The gravitational field is described by the field lines. A field line is the path followed by a free unit mass in that gravitational field A higher density of field lines a region of stronger field
8.2 Gravitational force between point masses b) recall and use Newton's law of gravitation in the form F r Gm m 2 1 2
Gravitational force between two point masses is proportional to the product of their masses & inversely proportional to the square of their separation F = GMm/r^2 4: Gravitational Field Constant 6.67 106++ Nm2kg-2
12.2 Internal energy and the first law of thermodynamics a) understand that internal energy is determined by the state of the system and that it can be expressed as the sum of a random distribution of kinetic and potential energies associated with the molecules of a system
Internal energy: sum of random distribution of kinetic and potential energies of molecules in a system Internal Energy = Total P.E. + Total K.E. A rise in temperature of a body is an increase in its internal energy
6.1 Energy conversion and conservation a) give examples of energy in different forms, its conversion and conservation, and apply the principle of conservation of energy to simple examples
Law of conservation of energy: the total energy of an isolated system cannot change—it is conserved over time. Energy can be neither created nor destroyed, but can change form e.g. from g.p.e to k.e
12.1 Specific heat capacity and specific latent heat a) explain using a simple kinetic model for matter: • the structure of solids, liquids and gases • why melting and boiling take place without a change in temperature • why the specific latent heat of vaporisation is higher than specific latent heat of fusion for the same substance • why a cooling effect accompanies evaporation
Melting & boiling occurs without change in temp.: o Temp. is a measure of random K.E. of the particles o At phase transition all energy used to break bonds o No change in K.E. occurs so temp. does NOT change Cooling effect of evaporation: o Particles which escape are those with higher velocity so average KE of remaining substance decreases o Temp. = average KE ∴ overall temperature decreases
5.2 Turning effects of forces a) define and apply the moment of a force
Moment of a Force: product of the force and the perpendicular distance of its line of action to the pivot 𝑀𝑜𝑚𝑒𝑛𝑡 = 𝐹𝑜𝑟𝑐𝑒 × ⊥ 𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑓𝑟𝑜𝑚 𝑃𝑖𝑣𝑜𝑡
8.3 Gravitational field of a point mass c) show an appreciation that on the surface of the Earth g is approximately constant
On Earth's surface, we can use the equation g.p.e = mgh however this is not true for masses far from Earth's surface because we assume g is constant
5.3 Equilibrium of forces a) state and apply the principle of moments
Principle of Moments: for a body to be in equilibrium, the sum of all the anticlockwise moments about any point must be equal to the sum of all the clockwise moments about that same point.
12.1 Specific heat capacity and specific latent heat c) define and use the concept of specific latent heat, and identify the main principles of its determination by electrical methods
Specific heat capacity: energy required per unit mass of the substance to raise the temperature by 1 Kelvin E=mc0
9.2 Elastic and plastic c) deduce the strain energy in a deformed material from the area under the force-extension graph
Strain energy: the potential energy stored in or work done by an object when it is deformed elastically Strain energy = area under force-extension graph 𝑊 = 1⁄2 𝑘Δ𝐿^2
9.1 Stress and strain c) define and use the terms stress, strain and the Young modulus
Stress: force applied per unit cross-sectional area 𝜎 =𝐹/𝐴 Strain: fractional increase in original length of wire 𝜀 =𝑒/𝑙 no units Young's Modulus: ratio of stress to strain 𝐸 =𝜎/𝜀= Stress/Strain = Fl/Ae
8.3 Gravitational field of a point mass b) recall and solve problems using the equation g r GM = 2 for the gravitational field strength of a point mass
The gravitational field strength at a point is the gravitational force exerted per unit mass By equating " % and Newton's Law of Gravitation mg = GMm /r^2 g=GM/r^2 By equating w=mg and Newton's Law of Gravitation
8.4 Gravitational potential a) define potential at a point as the work done per unit mass in bringing a small test mass from infinity to the point
The gravitational potential at a point is work done per unit mass in bringing a mass from infinity to the point O = -GM/r The negative sign is because: o Gravitational force is always attractive o Gravitational potential reduces to zero at infinity o Gravitational potential decreases in direction of field
11.1 Thermal equilibrium a) appreciate that (thermal) energy is transferred from a region of higher temperature to a region of lower temperature
Thermal energy is transferred from a region of higher temperature to a region of lower temperature
5.2 Turning effects of forces c) define and apply the torque of a couple
Torque of a Couple: the product of one of the forces of the couple and the perpendicular distance between the lines of action of the forces. 𝑇𝑜𝑟𝑞𝑢𝑒 = 𝐹𝑜𝑟𝑐𝑒 × ⊥ 𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒 𝑏𝑒𝑡𝑤𝑒𝑒𝑛 𝐹𝑜𝑟𝑐𝑒𝑠
5.1 Types of force b) understand the origin of the upthrust acting on a body in a fluid
Upthrust: an upward force exerted by a fluid on a submerged or floating object Origin of Upthrust: Pressure on Bottom Surface > Pressure on Top Surface ∴ Force on Bottom Surface > Force on Top Surface ⇒ Resultant force upwards
6.2 Work and efficiency a) understand the concept of work in terms of the product of a force and displacement in the direction of the force
Work done by a force: the product of the force and displacement in the direction of the force 𝑊 = 𝐹𝑠
6.2 Work and efficiency b) calculate the work done in a number of situations including the work done by a gas that is expanding against a constant external pressure: W = pDV
Work done by an expanding gas: the product of the force and the change in volume of gas 𝑊 = 𝑝. 𝛿𝑉 o Condition for formula: temperature of gas is constant o The change in distance of the piston, 𝛿𝑥, is very small therefore it is assumed that 𝑝 remains constant
4.3 Linear momentum and its conservation b) apply the principle of conservation of momentum to solve simple problems, including elastic and inelastic interactions between bodies in both one and two dimensions (knowledge of the concept of coefficient of restitution is not required)
(Perfectly) elastic collision: Both momentum & kinetic energy of the system are conserved. Inelastic collision: Only momentum is conserved, total kinetic energy is not conserved. Perfectly inelastic collision: Only momentum is conserved, and the particles stick together after collision. (i.e. move with the same velocity.)
9.2 Elastic and plastic behavior b) understand that the area under the force-extension graph represents the work done
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1.3 The Avogadro constant a) understand that the Avogadro constant NA is the number of atoms in 0.012 kg of carbon-12
1 mole of any subtance is the amount of that subtance which contain the same number of particles as there are in 12g of Carbon-12 I mol of a subtance contain 6.02 x 10^23
1.1 Physical quantities b)(4) make reasonable estimate of 1)Mass of 3 cans (330 ml) of Coke 2)Mass of a medium-sized car 3)Length of a football field 4)Reaction time of a young man
1)1 kg 2)1000 kg 3)100 m 4)0.2 s
1.1 Physical quantities b)(5) make reasonable estimate of 1)Mass of 3 cans (330 ml) of Coke 2)Mass of a medium-sized car 3)Length of a football field 4)Reaction time of a young man
1)1 kg 2)1000 kg 3)100 m 4)0.2 s
2.2 Errors and uncertainties a) understand and explain the effects of systematic errors (including zero errors) and random errors in measurements
1)Systematic Error -Its results in all the readings taken being faulty in one direction -Systematic Error cannot be eliminated by taking repeated readings and averaging them since the error will remain constant -It is an error that already exists in an instrument Examples: 1)Zero Error 2)Wrongly calibrated scale 2)Random Error -Its results in all readings taken being scattered about a mid-value -Cannot be eliminated but it can be minimized by taking repeated readings Examples: 1)Parallax Error 2)Reading Scales from different angles 3)Reaction Time
1.2 SI units a) recall the following SI base quantities and their units:
1)mass (kg), 2)length(m), 3)time (s), 4)current (A), 5)temperature (K), 6)amount of substance (mol)
3.1 Equations of motion f) derive, from the definitions of velocity and acceleration, equations that represent uniformly accelerated motion in a straight line
1. v = u +a t: derived from definition of acceleration: a = (v - u) / t 2. s = ½ (u + v) t: derived from the area under the v-t graph 3. v2 = u2 + 2 a s: derived from equations (1) and (2) 4. s = u t + ½ a t2: derived from equations (1) and (2) These equations apply only if (1)the motion takes place along a straight line (2)the acceleration is constant {hence, for eg., air resistance must be negligible.}
7.1 Kinematics of uniform circular motion a) define the radian and express angular displacement in radians
1.1 Radians Radian: one radian is the angle subtended at the center of the circle by an arc of length equal to the radius of the circle Angular displacement: the angle through which an object moves through a circle S=r0
10.3 Kinetic energy of a molecule a) recall that the Boltzmann constant k is given by the expression k = R / Na
3/2kT = E
d) use the equation Dp = ρgDh c) derive, from the definitions of pressure and density, the equation Δp = ρgDh
5.2 Derivation of Pressure in Fluids Volume of water = 𝐴 × ℎ Mass of Water = density × volume = 𝜌 × 𝐴 × ℎ Weight of Water = mass × 𝑔 = 𝜌 × 𝐴 × ℎ × 𝑔 Pressure = Force/Area= 𝜌×𝐴×ℎ×𝑔 / 𝐴 Pressure = 𝜌𝑔ℎ
6.3 Potential energy and kinetic energy a) derive, from the equations of motion, the formula for kinetic energy E 2mv 1 2
6.2 Deriving Kinetic Energy 𝑊 = 𝐹𝑠 & 𝐹 = 𝑚𝑎 ∴ 𝑊 = 𝑚𝑎. 𝑠 𝑣2 = 𝑢2 + 2𝑎𝑠 ⟹ 𝑎𝑠 = 1⁄2 (𝑣2 − 𝑢2) ∴ 𝑊 = 𝑚. 1⁄2 (𝑣2 − 𝑢2) 𝑢 = 0 ∴ 𝑊 = 1⁄2𝑚𝑣2
6.3 Potential energy and kinetic energy e) derive, from the defining equation W = Fs, the formula DEp = mgDh for potential energy changes near the Earth's surface
6.4 Deriving Gravitational Potential Energy 𝑊 = 𝐹𝑠 & 𝑤 = 𝑚𝑔 = 𝐹 ∴ 𝑊 = 𝑚𝑔. 𝑠 𝑠 in direction of force = ℎ above ground ∴ 𝑊 = 𝑚𝑔ℎ
6.4 Power a) define power as work done per unit time and derive power as the product of force and velocity
6.6 Power and a Derivation Power: work done per unit of time 𝑃𝑜𝑤𝑒𝑟 = 𝑊𝑜𝑟𝑘 𝐷𝑜𝑛𝑒 𝑇𝑖𝑚𝑒 𝑇𝑎𝑘𝑒𝑛 Deriving it to form 𝑃 = 𝑓𝑣 𝑃 = 𝑊. 𝑑⁄𝑇 & 𝑊. 𝑑.= 𝐹𝑠 ∴ 𝑃 = 𝐹𝑠⁄𝑇 = 𝐹(𝑠⁄𝑡) & 𝑣 = 𝑠⁄𝑡 ∴ 𝑃 = 𝐹𝑣
1.1 Physical quantities b)(3) make reasonable estimate of The Mass Of The Plastic 30cm Ruler:
=> A plastic ruler cannot have mass greater or equal to KG. But a 500 gram object will obviously be much heavier than a plastic ruler. So, it must be in the range of 30g to 100g. Answer: 50g
1.1 Physical quantities b)(4) make reasonable estimate of Density Of Air At Atmospheric
=> As we know the value of Atmospheric pressure if approximately 100,000 pascals. Let's consider the height of the air that surrounds the earth is 10000m. Now using the formula Pressure = density * gravity * height, we can find out the density. Density: 1 Kg/m^3
1.1 Physical quantities b)(2) make reasonable estimate of The Wavelength, in nm, of Ultraviolet Radiation:
=> If you remember the Order Of Magnitude of electromagnetic radiation then you can answer this question easily. Ultraviolet radiation has wavelength from meter. So you can put any value between this. Answer: 50nm
1.4 Scalars and vectors a) distinguish between scalar and vector quantities and give examples of each
A scalar quantity has a magnitude only. It is completely described by a certain number and a unit. Examples:- Distance, speed, mass, time, temperature, work done, kinetic energy, pressure, power, electric charge etc. A vector quantity has both magnitude and direction. It can be described by an arrow whose length represents the magnitude of the vector and the arrow-head represents the direction of the vector. Examples:- Displacement, velocity, moments (or torque), momentum, force, electric field etc.
1.1 Physical quantities b)(7)Which estimate is realistic? A)The kinetic energy of a bus travelling on an expressway is 30000J B)The power of a domestic light is 300W. C)The temperature of a hot oven is 300 K D)The volume of air in a car tyre is 0.03 m^3.
A)A bus of mass m travelling on an expressway will travel between 50 to 80 kmh-1, which is 13.8 to 22.2 ms-1. Thus, its KE will be approximately ½ m(182) = 162m. Thus, for its KE to be 30000J: 162m = 30000. Thus, m = 185kg, which is an absurd weight for a bus; ie. This is not a realistic estimate. B)A single light bulb in the house usually runs at about 20W to 60W. Thus, a domestic light is unlikely to run at more than 200W; this estimate is rather high. C)300K = 27 0C. Not very hot. D)Estimating the width of a tyre, t, is 15 cm or 0.15 m, and estimating R to be 40 cm and r to be 30 cm, volume of air in a car tyre is = π(R2 - r2)t = π(0.42 - 0.32)(0.15) = 0.033 m3 ≈ 0.03 m3 (to one sig. fig.)
2.2 Errors and uncertainties c) assess the uncertainty in a derived quantity by simple addition of absolute, fractional or percentage uncertainties (a rigorous statistical treatment is not required)
Actual error must be recorded to only 1 significant figure, & The number of decimal places a calculated quantity should have is determined by its actual error. For eg, suppose g has been initially calculated to be 9.80645 m s-2 & g has been initially calculated to be 0.04848 m s-2. The final value of g must be recorded as 0.05 m s-2 {1 sf }, and the appropriate recording of g is (9.81 0.05) m s-2.
1.2 SI units c) use SI base units to check the homogeneity of physical equations
An equation is homogeneous if quantities on BOTH sides of the equation has the same unit • E.g. s = ut + ½ at2 • LHS : unit of s = m • RHS : unit of ut = ms-1 x s = m • unit of at2 = ms-2 x s^2 = m • Unit on LHS = unit on RHS • Hence equation is homogeneous P = ρgh2 • LHS ; unit of P = Nm-2 = kg m-1 s-2 • RHS : unit of ρgh2 = kg m-3(ms-2) (m^2) = kgs-2 • Unit on LHS =(not) unit on RHS • Hence equation is not homogeneous • Note: numbers has no unit • some constants have no unit. • e.g. Pi
10.2 Kinetic theory of gases b) state the basic assumptions of the kinetic theory of gases
Basic Assumptions of the Kinetic Theory of Gases Gas contains large no. of particles Negligible intermolecular forces of attraction Volume of particles negligible compared to container Collisions between particles are perfectly elastic No time spent in collisions Average k.e. directly proportional to absolute temp.
7.2 Centripetal acceleration and centripetal force b) recall and use centripetal acceleration equations a = r~2 and a r v2
Centripetal acceleration: derived by equating Newton's 2nd law and centripetal force a = r * w^2 or a = v^2/r
3.1 Equations of motion a) define and use distance, displacement, speed, velocity and acceleration
Distance: Total length covered irrespective of the direction of motion. Displacement: Distance moved in a certain/specified direction Speed: Distance travelled per unit time. Velocity: is defined as the rate of change of displacement, or, displacement per unit time {NOT: displacement over time, nor, displacement per second, nor, rate of change of displacement per unit time} Acceleration: is defined as the rate of change of velocity.
4.3 Linear momentum and its conservation c) recognise that, for a perfectly elastic collision, the relative speed of approach is equal to the relative speed of separation
For all elastic collisions, u1 - u2 = v2 - v1 ie. relative speed of approach = relative speed of separation or, ½ m1u1^2 + ½ m2u2^2 = ½ m1v1^2 + ½ m2v2^2
4.1 Momentum and Newton's laws of motion d) define and use force as rate of change of momentum
Force is defined as the rate of change of momentum F = m(v - u)/t = ma F = v dm/dt The {one} Newton is defined as the force needed to accelerate a mass of 1 kg by 1 m s-2.
1.1 Physical quantities b)(1) make reasonable estimate of Frequency Of Audible Sound Wave:
Humans can detect sounds in a frequency range from about 20 Hz to 20 kHz. (Human infants can actually hear frequencies slightly higher than 20 kHz, but lose some high-frequency sensitivity as they mature; the upper limit in average adults is often closer to 15-17 kHz.)
13.1 Simple harmonic oscillations a) describe simple examples of free oscillations
In free oscillation, a body oscillate at its natural frequency and its natural frequency and is unaffected by external forces, the total energy of the freely oscillating system remains constant. Eg: The vibrating string of a guitar, a simple pendulum oscillating in air
4.3 Linear momentum and its conservation d) understand that, while momentum of a system is always conserved in interactions between bodies, some change in kinetic energy may take place
In inelastic collisions, total energy is conserved but Kinetic Energy may be converted into other forms of energy such as sound and heat energy.
6.4 Power b) solve problems using the relationships P t W = and P = Fv
LOGIC
7.1 Kinematics of uniform circular motion c) recall and use v = r~ to solve problems
LOGIC Period: the time taken by the body to complete the circular path once W = 2*PIE/T = 2*PIE*F Relating angular velocity and linear velocity: V = WR
4.1 Momentum and Newton's laws of motion c) Define linear momentum and impulse.
Linear momentum of a body is defined as the product of its mass and velocity. p = m v Impulse of a force I is defined as the product of the force and the time t during which it acts Impulse = F x t = mv - mu = chnage in momentum {for force which is const over the duration t} For a variable force, the impulse = Area under the F-t graph { Fdt; may need to "count squares"} Impulse is equal in magnitude to the change in momentum of the body acted on by the force. Hence the change in momentum of the body is equal in mag to the area under a (net) force-time graph. {Incorrect to define impulse as change in momentum}
4.1 Momentum and Newton's laws of motion a) understand that mass is the property of a body that resists change in motion
Mass: is a measure of the amount of matter in a body, & is the property of a body which resists change in motion.
4.1 Momentum and Newton's laws of motion e) state and apply each of Newton's laws of motion
Newton‟s First Law Every body continues in a state of rest or uniform motion in a straight line unless a net (external) force acts on it. Newton‟s Second Law The rate of change of momentum of a body is directly proportional to the net force acting on the body, and the momentum change takes place in the direction of the net force. Newton‟s Third Law When object X exerts a force on object Y, object Y exerts a force of the same type that is equal in magnitude and opposite in direction on object X. The two forces ALWAYS act on different objects and they form an action-reaction pair.
10.2 Kinetic theory of gases c) explain how molecular movement causes the pressure exerted by a gas and hence deduce the relationship pV 3Nm c = 1 2 , where N = number of molecules [A simple model considering one-dimensional collisions and then extending to three dimensions using 3 c cx 1 2 = 2 is sufficient.]
PHOTO
9.1 Stress and strain d) describe an experiment to determine the Young modulus of a metal in the form of a wire
PHOTO
2.2 Errors and uncertainties b) understand the distinction between precision and accuracy
Precision: refers to the degree of agreement (scatter, spread) of repeated measurements of the same quantity. {NB: regardless of whether or not they are correct.} Minimizing Random error is Precision Accuracy refers to the degree of agreement between the result of a measurement and the true value of the quantity. Minimizing or Eliminating Systematic error is Accuracy
4.3 Linear momentum and its conservation a) state the principle of conservation of momentum
Principle of Conservation of Linear Momentum: When objects of a system interact, their total momentum before and after interaction are equal if no net (external) force acts on the system. The total momentum of an isolated system is constant m1 u1 + m2 u2 = m1 v1 + m2 v2 if net F = 0 {for all collisions } NB: Total momentum DURING the interaction/collision is also conserved.
11.2 Temperature scales c) convert temperatures measured in kelvin to degrees Celsius and recall that
T / K = T / °C + 273.15
9.1 Stress and strain a) appreciate that deformation is caused by a force and that, in one dimension, the deformation can be tensile or compressive
Tensile= act away from each other object stretched out. Compressive= Act towards each other object squashed.
3.1 Equations of motion c) determine displacement from the area under a velocity-time graph
The area under a velocity-time graph is the change in displacement.
3.1 Equations of motion d) determine velocity using the gradient of a displacement-time graph
The gradient of a displacement-time graph is the {instantaneous} velocity.
3.1 Equations of motion e) determine acceleration using the gradient of a velocity-time graph
The gradient of a velocity-time graph is the acceleration.
11.3 Practical thermometers a) compare the relative advantages and disadvantages of thermistor and thermocouple thermometers as previously calibrated instruments
Thermistor Advantages: Very robust Fast response Accurate Sensitive at low temps Disadvantages: Narrower range Slower response time than thermocouple Larger thermal capacity Larger in size Not suitable to measure varying temp. THERMOCOUPLE: Advantages Faster response Wider range Small thermal capacity Physically small - readings taken at point Power supply not need Disadvantages: For accurate reading, a high resistance voltmeter required
4.2 Non-uniform motion a) describe and use the concept of weight as the effect of a gravitational field on a mass and recall that the weight of a body is equal to the product of its mass and the acceleration of free fall
Weight: is the force of gravitational attraction (exerted by the Earth) on a body.
1.2 SI units d) use the following prefixes and their symbols to indicate decimal submultiples or multiples of both base and derived units: pico (p), nano(n), micro (μ), milli (m), centi (c), deci (d), kilo (k), mega (M), giga (G), tera(T)
pico (p), 10^-12 nano(n), 10^-9 micro (μ), 10^-6 milli (m), 10^-3 centi (c), 10^-2 deci (d), 10^-1 kilo (k), 10^3 mega (M), 10^6 giga (G), 10^9 tera(T), 10^12
1.1 Physical quantities b)(6)Estimate the average running speed of a typical 17-year-old‟s 2.4-km run.
velocity = distance / time =2400 / (12.5 x 60) = 3.2 ≈3 ms-1
