Teach9 - Rethinking Eduction

Bringing together students of all levels from across the world – come and answer your peers’ educational questions, find answers to those difficult homework tasks and create your growing profile to propel your education and skills to new heights.

Sign Up Now
How it Works
Fillter Close

The forward motion of a motor-boat is opposed by forces F which vary with the boat’s speed v in accordance with the relation F = k v 2 , where k is a constant. The effective power of the propellers required to maintain the speed v is P. Which expression relates k, P and v ?

K = P/V^3

An object, made from two equal masses joined by a light rod, falls with uniform speed through air. The rod remains horizontal. Which statement about the equilibrium of the system is correct?

t is in equilibrium because there is no resultant force and no resultant torque.

Which statement about Newton’s laws of motion is correct?

The first law follows from the second law.

What is the approximate mass of a nucleus of uranium?

10^-25 kg is the approximate mass of a nucleus of uranium

The potential difference across a resistor is 12V. The current in the resistor is 2.0A. 4.0C passes through the resistor. What is the energy transferred and the time taken?

The energy transferred is 48 J and the time taken is 2 seconds

A total charge of 100C flows through a 12W light bulb in a time of 50s. What is the potential difference across the bulb during this time?

6.0 V is the potential difference across the bulb during this time.

Light of wavelength 700nm is incident on a pair of slits, forming fringes 3.0mm apart on a screen. What is the fringe spacing when light of wavelength 350 nm is used and the slit separation is doubled?

The fringe spacing is 0.75 mm when light of wavelength 350 nm is used and the slit separation is doubled.

Sound waves, emitted by a small loudspeaker, are reflected by a wall. The frequency f of the waves is adjusted until a stationary wave is formed with the antinode nearest the wall at a distance x from the wall. Which expression gives f in terms of x and the speed of sound c?

F = c / 4x

The formula for hydrostatic pressure is p = ρgh. Which equation, or principle of physics, is used in the derivation of this formula?

density = mass ÷ volume is used in the derivation of this formula

Why does an ideal gas exert pressure on its container?

an ideal gas exerts pressure on its container because the molecules of the gas collide continually with the walls of the container.

Which quantities are conserved in an inelastic collision?

In an inelastic collision kinetic energy is not conserved, the total energy is conserved and the linear momentum is conserved as well

A ball is falling at terminal speed in still air. The forces acting on the ball are upthrust, viscous drag and weight. What is the order of increasing magnitude of these three forces?

upthrust → viscous drag → weight is the order of increasing magnitude of these forces

Which is a statement of the principle of conservation of momentum?

Momentum is conserved providing no external forces act.

An object accelerates in a direction that is always perpendicular to its motion. What is the effect, if any, of the acceleration on the object’s speed and direction?

The effect of the acceleration on the object speed is that speed is constant and the direction changes.

What is a reasonable estimate of the average kinetic energy of an athlete during a 100 m race that takes 10s?

4000 J is the estimate of the average kinetic energy of an athelete during a 100m race that takes 10s

Over half a million tonnes of bromine are manufactured annually and are mainly used for making other compounds. One important use is for agricultural chemicals. What is another important use for bromine?

another important use for bromine is flame-retardants and fire extinguishers.

In some fireworks there is a reaction between powdered aluminium and powdered barium nitrate in which heat is evolved and an un reactive gas is produced. What is the equation for this reaction?

The equation for this reaction is 10Al + 3Ba(NO3)2 → 5Al2O3 + 3BaO + 3N2

When copper is extracted from its ores, the metal is not pure enough for electrical uses. The impure copper, which contains small amounts of silver and gold, is purified by electrolysis. During this process a ‘sludge’ forms beneath the anode which is found to contain silver and traces of gold. Why is silver found in this sludge?

Silver is found in this sludge because Silver is less electropositive than copper.

In which reaction does the carbon-containing product have a smaller bond angle than the organic reactant?

polymerisation of ethane does the carbon-containing product have a smaller bond angle than the organic reactan

The first seven ionisation energies of an element between lithium and neon in the Periodic Table are as follows. 1310 3390 5320 7450 11 000 13 300 71 000 kJmol–1 What is the outer electronic configuration of the element?

the outer electronic configuration of the element is 2s2 2p4

Compound X, C6H12O, is oxidised by acidified sodium dichromate(VI) to compound Y. Compound Y reacts with ethanol in the presence of a little concentrated sulphuric acid to give liquid Z. What is the formula of Z?

The formula of Z is CH3(CH2)4CO2CH2CH3

Ethanal, CH3CHO, can be reduced using an aqueous methanolic solution of NaBH4 as the reducing agent. This is a nucleophilic addition reaction. What could be the first step of this mechanism?

The first step of mechanism is attack of an H– ion at the carbon atom of the carbonyl group

An alcohol of molecular formula C4H10O2 contains two OH groups and has an unbranched carbon atom chain. On reaction with an excess of hot − MnO4 / H+ this alcohol is converted into a compound of molecular formula C4H6O4. To which two carbon atoms in the chain of the alcohol are the two OH groups attached?

to 1st and 4th carbon atoms in the chain of the alcohol are the two OH groups attached

Chloroethene, CH2=CHCl, is the monomer of PVC. What are the C−C−C bond angles along the polymeric chain in PVC?

They are all 109.5° along the polymeric chain in PVC

Total elimination of the pollutant sulphur dioxide, SO2, is difficult, both for economic and technical reasons. Its emission can be reduced in furnace chimneys using desulphurisation plants, where the gases are scrubbed (washed) with calcium hydroxide to remove the SO2. What is the main product formed initially?

CaSO3 is formed initially

Properties of chlorine, iodine and their compounds are compared. Property Q for chlorine is smaller than for iodine. What is property Q?

strength of van der Waals’ forces between the molecules of the element is the property of Q

Which element is expected to show the greatest tendency to form some covalent compounds?

aluminium is expected to show the greatest tendency to form some covalent compounds

In an experiment, 0.1 g samples of Na2O, MgO, P4O10 and SO2 are added to separate 100 cm3 volumes of water. For which oxide is the resulting mixture most alkaline?

For Na2O the resulting mixture most alkaline

Which pair of elements have bonds of the same type between their atoms in the solid state?

sulphur and chlorine have bonds of the same type between their atoms in the solid state

What would increase the price elasticity of supply of a firm’s products?

a decrease in the time that it takes to produce the products would increase the price elasticity of supply of a firm products.

A good has unitary price elasticity of demand and at a price of $25 it sells 100 000 units. Which price must the firm charge if it wants to sell 125 000 units of the good?

$ 20 price must the firm charge if it wants to sell 125 000 units of the good

The demand for a product is affected by a number of influences. What will cause a movement along its demand curve?

a rise in the price of the product will cause a movement along its demand curve.

What is not an essential characteristic of money?

It must have a intrinsic value is not an essential characteristic of money

A country with a freely floating exchange rate has a persistent deficit on the current account of its balance of payments. Which policy can be used to correct this disequilibrium?

increasing tax rates can be used to correct this disequilibrium.

According to the Purchasing Power Parity theory, what determines the rate of exchange between two countries?

The relative price levels in the two countries determine the rate of exchange between the two countries according to PPP Theory.

In which situation must a country’s balance of trade in goods and services improve?

when Export revenues rise more than import revenues a country’s balance of trade in goods and services improves

What would be likely to increase inflation in an economy?

an increase in taxes on imports would be likely to increase inflation in an economy

Which combination is likely to result from demand-pull inflation?

The balance of trade is worsening and the profits are rising simultaneously is likely to result from demand pull inflation.

A country’s terms of trade increased from the base year value of 100 to 120 in the following year. Which behaviour of export prices and import prices would have caused this?

The export price have increased to 20% where as the import prices are unchanged.

Which method of protection would a government be most likely to use to increase the country’s exports?

Subsidies is a method of protection that a government would be most likely to use to increase the country’s exports

For which one of the following reasons might education be considered a merit good?

education might be considered a merit good because, It benefits both the recipient and society as a whole.

Vandalism and crime have increased in an area of a city following the opening of a night club. As a result, additional police have been sent to patrol the area. What does this statement illustrate?

This statement illustrates a negative externality and a public good which is night club.

A village has improved its supply of clean water, sewage treatment, insect control and milk pasteurisation. Which disease, present in the village, will not be reduced by these measures?

HIV/AIDS disease will not be reduced by these measures.

What is an effect of inhaling tobacco smoke?

The effect of inhaling tobacco smoke is that there is reduced oxygen transport by blood.

What is the main function of a companion cell in mature phloem tissue?

the main function of a companion cell in mature phloem tissue is providing cytoplasmic contact with the sieve tube for loading

Normal venous pressure in the feet is 3.3 kPa. When a person stands very still venous blood pressure in the feet rises to 5.0kPa. What causes the high pressure?

Skeletal muscles in the legs are not squeezing blood upward in the veins causes the high pressure.

Which type of tissue is present in the walls of all blood vessels?

endothelial tissue is present in the walls of all blood vessels.

which statement correctly describes the transcription of DNA?

it produces messenger RNA describes transcription of DNA

What happens to chromosomes in prophase of mitosis?

They shorten and become visible

During which process does mitosis occur?

during the production of cancerous tissue in alveoli mitosis occur

Which molecule prevents the cell surface membrane from becoming too fluid or too rigid?

cholesterol prevents the cell surface membrane from becoming too fluid or too rigid

Which property of water minimises temperature changes in cells and organisms?

specific heat capacity of water minimises temperature changes in cells and organisms

For which process is the large surface area of the cristae in the mitochondria important?

for enzyme reaction process the large surface area of cristae is the mitochondria important.

What is a function of the smooth endoplasmic reticulum?

synthesis of steroids is a function of the smooth endoplasmic reticulum.

What describes resolution in microscopy?

the ability to distinguish between two objects that are very close together describes resolution in microscopy

A lysosome measures 0.4µm in diameter. What is the diameter in nm?

400 nm is the diameter.

What identifies a cell as a prokaryote?

The DNA is in a circular form identifies a cell as a prokaryote

Each of the nuclei below is accelerated from rest through the same potential difference. Which one completes the acceleration with the lowest speed?

7/3 Li completes the acceleration with the lowest speed.

A detector is exposed to a radioactive source. Fluctuations in the count-rate are observed. What do these fluctuations indicate about radioactive decay?

radioactive decay is random these fluctuations indicate.

The current in a resistor is 8.0mA. What charge flows through the resistor in 0.020s?

The charge that flows through the resistor in 0.020s is 0.16mC

What is a correct statement of Ohm’s law?

The potential difference across a component is proportional to the current in it providing physical conditions stay constant is a correct statement of Ohm’s Law

The electric field strength between a pair of parallel plates is E. The separation of the plates is doubled and the potential difference between the plates is increased by a factor of four. What is the new electric field strength?

2E is the new electric field strength.

A two-slit arrangement is set up to produce interference fringes on a screen. The fringes are too close together for convenient observation when a monochromatic source of violet light is used. In which way would it be possible to increase the separation of the fringes?

By using a monochromatic source of red light, it would be possible to increase the separation of the fringes

Sound wave X has intensity 10^12 times greater than that of sound wave Y. By how much is the amplitude of X greater than the amplitude of Y?

10^6 times is the amplitude of X greater than the amplitude of Y

Which of the following types of wave can be polarised?

a transverse stationary wave can be polarised.

A piece of copper is drawn into a continuous wire. What behaviour is the copper exhibiting?

The copper is exhibiting plastic only.

What is meant by the weight of an object?

The weight of an object means the gravitational force acting on the object

What gives the value of a body’s acceleration?

the gradient of its velocity-time graph gives the value of a body’s acceleration.

Which is a pair of SI base units?

kilogram and Kelvin is a pair of SI base units

What is a correct order of magnitude estimate for the diameter of a typical atomic nucleus?

10–14 m is a correct order of magnitude estimate for the diameter of a typical atomic nucleus

Which equation is used to define resistance?

potential difference = current × resistance defines resistance.

Which consequence of building an underground railway line would be classified as an externality?

a reduction in road accidents of building an underground railway line would be classified as an externality

In 2006, some tobacco companies in china wanted to raise prices but a spokesman said the tobacco industry was no longer in a position where it could increase revenue by raising prices. What might be concluded from this statement?

The reason for this is that the quantity of labour is uncertain and the quantity of capital would increase.

Goods X and Y are complements. What will be the effect on the equilibrium price and quantity of good X of an increase in the supply of good Y?

The equilibrium price and quantity of X both will increase with an increase in the supply of good Y

A businessman had intended to borrow $5000 at 8 % per year for house purchase. When the interest rate rose to 10% he decided to borrow only $4000. Within what range is his interest elasticity of demand for loans?

–0.8 to –1.2 range is his interest elasticity of demand for loans

What ensures that demand for a product is effective?

The consumer must have sufficient income to buy the product ensures that demand for a product is effective

A farmer can produce both beef and lamb. The opportunity cost of a kilo of beef is three kilos of lamb. The price of a kilo of beef is twice that of lamb. What should he do if his aim is to maximise his revenue?

if his aim is to maximise his revenue than the farmer should concentrate on lamb production.

What is necessarily a function of enterprise rather than management?

accepting the risks involved in production is necessarily a function of enterprise rather than management

Planned economies had a history of failing to produce enough consumer goods. Which method of allocating these goods in short supply involved a market system approach?

unofficial sale to people according to their willingness to pay will allocate these goods in short supply in a market system

In an attempt to correct a balance of trade deficit the government of South Africa has decided to employ expenditure-dampening methods. Which policy would best fit this description?

Raising income tax rates policy would best fit this description. Since people will spend less and when they spend less expenditure will be dampened which will help achieve objectives.

Increased international competition leads to a worsening in a country’s current account balance. In the absence of any offsetting factors, how is this likely to affect domestic inflation and the exchange rate?

The domestic inflation decrease and the exchange rate increases.

What might explain an increase in the volume of a country’s imports?

an appreciation of the country’s exchange rate might explain an increase in the volume of a country’s imports