This is a great “technical practical” that you can use to investigate how a lever works, but in a fun practical way. It requires some tricky kit, so you might need to go do to the local tyre shop to see if they will let you have a go!
Equipment…
Force Sensor (range 0.1N to 500N) (link – for suggested type of sensor)
Safety: to avoid cuts or crushing injury wear gloves and heavy duty shoes, in case your hands slip on the lever as you apply forces.
Method
Calibrate a resistance based force sensor using weights and a multi-meter set to ohms. Create a graph so you can convert resistance to a specific force.
Put car wheel on the floor on its side.
Glue a force sensor to the tyre lever on the top of the “load side”
Put markings for distance on a tyre lever every 0.05m from the pivot point and pivot point itself.
Hold the lever with one hand at the nearest point to the pivot, apply enough force to pull the rubber over the rim.
Record the distance, reading on the multimeter in a table then use the graph to convert to a load force which should also be recorded.
Replace the rubber and repeat steps 5 and 6 but 0.05m further away. Record all the results in a table.
Graph the load force v distance from pivot and look for a pattern.
Repeat with a 2nd wheel and compare graphs.
Control Variables
During the experiment you must control certain factors. You hand must not slip or move from the distance to the pivot
Force sensor must not change angle against the rim or tyre or the results will vary for the resistance
Pivot point must stay fixed
Temperature may have an effect on the force sensor so all results must be collected on the same day and in the same place.
Here are a set of resources to help with iGCSE forces and Astronomy Section. The syllabus aims are shown below and also all the resources for the lesson. The idea is to have a printed version of the PPT ideally or use on a PC where you can edit it, or view on a tablet. As you work through the activities you should have a 2nd browser tab open for the quiz, and work through the questions as you go. Also linked from the quiz are some breakout videos to view if you get stuck. I would also suggest you download a QR Code reader so you can find any links quickly.
Syllabus…
1.32 Understand gravitational field strength, g, and recall that it is different on other planets and the moon from that on the Earth
1.33 Explain that gravitational force:
causes moons to orbit planets
causes the planets to orbit the sun
causes artificial satellites to orbit the Earth
causes comets to orbit the sun
1.34 Describe the differences in the orbits of comets, moons and planets
1.35 Use the relationship between orbital speed, orbital radius and time period
1.36 Understand that:
the universe is a large collection of billions of galaxies
a galaxy is a large collection of billions of stars
Sky lights up over Sicily as Mount Etna’s Voragine crater erupts
Display of volcanic lightning inside giant smoke and ash cloud over Europe’s tallest active volcano is Voragine crater’s first eruption in two years. The night sky lights up over the east coast of Sicily as Mount Etna’s Voragine crater erupts for the first time in two years. The giant plume of smoke and ash thrown up by the blast creates a dazzling display of volcanic lightning, a mysterious phenomenon seen in many of the most powerful volcanic eruptions.
It is thought that ash particles rubbing together inside the cloud could lead to the buildup of an electric charge that triggers the lightning strikes, much as a weak charge builds up on a balloon rubbed on a jumper
When the Icelandic volcano Eyjafjallajökull erupted in 2010, the combination of dust with ice and water from an overlying glacier produced a spectacular “dirty thunderstorm” that sent streaks of lightning leaping around inside the plume that drifted overhead.
The tallest active volcano in Europe, Mount Etna stands 3329m high and has been erupting for an estimated 2.5m years. In modern times, towns and villages in the foothills of Etna have been protected by ditches and concrete dams that divert lava flows to safer ground. The volcano has five craters: the Bocca Nuova, the north-east crater, two in the south-east crater complex and the Voragine. The Voragine crater formed inside the volcano’s central crater in 1945.
Volcanic activity in the region is driven by the collision of the African tectonic plate with the Eurasian plate. Magma from molten rock erupts as lava and ash and builds the volcano in the process.
Turbo gives petrol cars a boost as diesel faces backlash
Looking at Kia’s new Proceed T-GDi GT-Line, with its sporty looks and handling, you might expect a big, thirsty engine under the bonnet.
Instead, it has a frugal three-cylinder 1.0 litre petrol engine that can still deliver 0-62mph (0-100km/h) in 10.7 seconds, nearly 60 miles to the gallon, and CO2 emissions of 115g/km.
A few years ago, this kind of performance would’ve been considered outstanding.
Thanks to turbo tech, these traditionally-fuelled internal combustion engines are now offering better fuel economy and lower emissions, without comparable loss of performance.
“Diesel has emerged as the dominant fuel type for company cars, as a result of great fuel efficiency, performance and low cost of ownership under the government’s CO2 emissions based tax regime,” says Gerry Keaney, chief executive of the British Vehicle Rentals and Leasing Association, whose members own or fleet manage more than three million cars in the UK.
“But the diesel proportion of new registrations has been falling gradually for some time, as modern petrol powered cars have become better at delivering similar benefits, and we expect this trend to gather pace.”
In the UK, even company car buyers now see downsized petrol engines, many emitting around 100g/km CO2, as a viable, efficient alternative to diesel.
This is not just down to “anti-diesel sentiment”, says Al Bedwell, director, global powertrains at LMC Automotive. “It has more to do with petrol getting better and staging a fight-back, especially in small cars in Western Europe.”
Manufacturers such as Ford, Opel/Vauxhall, Hyundai and Volkswagen are all offering similarly downsized petrol engines these days, many emitting around 100g/km of CO2.
In Europe, diesel’s share of the market is set to drop from 53.3% of the market in 2014 to 51.5% in 2015, says Mr Bedwell, then continue sliding to 35% by 2020.
Power boost
Turbo chargers are traditionally associated with diesel engines, which needed a boost to give them more oomph. They weren’t “much fun to drive” without them, says Guillaume Devauchelle, head of innovation and science at automotive technology company, Valeo.
And the relative cost of adding turbo to an expensive diesel engine was lower, he explains.
Image copyrightGetty Images
But turbos are now increasingly infiltrating petrol engines because they deliver dramatic emissions reductions and improvements in fuel economy, without sacrificing performance, says Craig Balis, chief technology officer of Honeywell Transportation Systems, the world’s largest turbo maker.
A two-litre turbo-charged four cylinder petrol engine can match the output of a three-litre naturally aspirated V6 petrol engine, he says, so “the technology we have is really a no-compromise solution”.
Turbos work by using the engine’s exhaust gas to drive a turbine, which in turn drives a compressor, which compresses air. This air is then forced into the combustion chamber where it mixes with fuel to create additional power.
This means the engine won’t have to burn so much fuel to deliver the same output.
“Our turbos for passenger vehicles have turbines that spin at 200,000-300,000 revolutions per minute (rpm), generating temperatures of up to 1,000 degrees Celsius, so the metal is literally glowing red,” Mr Balis says.
By comparison petrol engines operate at just 6,000-7,000 rpm and diesel at 5,000-6,000rpm.
To cope with such extreme speed, pressure and heat, turbos need to be incredibly robust, so Honeywell is using ball bearings and other technologies that have been developed for military aircraft by the company’s aerospace division.
The turbos are also coupled with intercoolers that cool the airflow and increases its density as it is supplied to the engine, and with oil cooling systems that prevent overheating.
Instant power
Turbos are often combined with direct or indirect fuel injectors and variable valve lift or timing systems to make the process even more efficient.
Electrified superchargers, which compress air for just a few hundred milliseconds to add brief low-end torque until the turbo charger kicks in, will also hit the market in the next few months.
Over the next five years, we’ll go from about a third to around half the cars sold having turbo chargers, and the growth will continue. We call this the ‘golden age of turbo’
Terrence Hahn, Honeywell TS
E-chargers, or e-turbos, will transform the driving experience, believes Mr Devauchelle, as they eliminate what’s called turbo lag – that slight delay in power boost you experience after pressing the accelerator.
“The turbo increases the engine’s maximum power. The e-charger gets you there even quicker,” he explains.
As such, e-turbos may rival established twin-turbo technology, where a small turbo takes care of the early stages of acceleration before the second turbo takes over.
The e-turbos’ batteries can be recharged in different ways, for instance by capturing energy during braking, explains Mr Hahn.
With enough electric power, e-chargers could take over more and more of the work done by the turbo.
Eventually carmakers will redesign vehicle architecture, moving from standard 12-volt batteries to higher voltage systems.
Forty-eight volt architecture is emerging in luxury cars with many electric components, but e-chargers can also run on 12-volt batteries if they are only required to deliver brief boosts, explains Mr Devauchelle.
‘Golden age of turbo’
“Petrol power is moving from naturally aspirated engines to turbo charged engines at a faster rate than ever before,” says Terrence Hahn, president and chief executive of Honeywell Transportation Systems.
“Over the next five years, we’ll go from about a third to around half the cars sold having turbo chargers, and the growth will continue,” he predicts.
“We call this ‘the golden age of turbo’.”
But there is no silver bullet as carmakers continue to grapple with ever-stricter emissions regulation, coupled with huge penalties for non-compliance.
Any number of combinations of e-chargers, turbo chargers, multi-stage boosting, fuel injection, variable valve systems, and combustion-electric hybrid technologies are being explored.
“During 30 years in the industry, I have never before seen so much diversity,” says Mr Devauchelle.
It’s nearly 50 years since the US landed men on the moon, but Americans are still dying from a disease that ravaged Europe in the Middle Ages. Why hasn’t the US eradicated the plague?
The Black Death caused about 50 million deaths across Africa, Asia and Europe in the 14th Century. It wiped out up to half of Europe’s population.
Its last terrifying outbreak in London was the Great Plague of 1665, which killed about a fifth of the city’s inhabitants. Then there was a 19th Century pandemic in China and India, which killed more than 12 million.
But the disease has not been consigned to the dustbin of history. It is endemic in Madagascar, the Democratic Republic of Congo and Peru. What’s perhaps more surprising is that it is still killing people in the US.
There have been 15 cases in the US so far this year – compared to an average of seven, according to the Centers for Disease Control and Prevention (CDC) – and the figure of four deaths is higher than in any year this century.
The bacterium responsible – Yersinia pestis – was introduced to the US by rat-infested steamships in 1900, according to Daniel Epstein of the World Health Organization (WHO).
“Plague was pretty prevalent, with epidemics in Western port cities. But the last urban plague was in Los Angeles in 1925. It spread to rural rats and mice, and that’s how it became entrenched in parts of the US,” he says.
The disease – typically transmitted from animals to humans by fleas – has a 30-to- 60% fatality rate if left untreated, however, antibiotics are effective if patients are diagnosed early.
The plague
Image copyrightScience Photo Library
More than 80% of US cases have been bubonic plague, the most common form, which affects the lymph nodes and causes gangrene (see picture at top of page)
There are two other types, septicaemic, an infection of the blood, and pneumonic, which infects the lungs
It can be hard to identify the disease in its early stages because symptoms, which usually develop after three to seven days, are flu-like – a laboratory test can confirm diagnosis
Most cases occur in summer, when people spend more time outdoors.
“The advice is, take precautions against flea bites and don’t handle animal carcasses in plague-endemic areas,” says Epstein.
The areas in question are New Mexico, Arizona, California and Colorado, according to the CDC. All of this year’s cases originated in those states, or in other states west of the 100th meridian, which Dr Amesh Adalja, an infectious-disease specialist at the University of Pittsburgh’s Center for Health Security, refers to as “the plague line”.
“Prairie dogs are the main reservoir for plague, and they tend to be west of the 100th meridian,” he says. The geography and climate of the Western US suits them, he explains, and the fact that they are “social animals” helps the infected fleas to spread.
Image copyrightGetty ImagesImage captionYersinia pestis thrives in prairie dogs’ fleas
Black-footed ferrets and the Canada lynx are other particularly susceptible species, says Dr Danielle Buttke, an epidemiologist at the US National Park Service.
It’s the existence of this “animal reservoir” that makes the plague hard, if not impossible, to eradicate, experts say.
The only human disease eradicated so far, smallpox, does not exist in animals. It’s the same with polio, which remains endemic in two countries – Afghanistan and Pakistan. The WHO is working towards to eradicating polio and last month announced that it is no longer endemic in Nigeria. (It has, however, returned to Syria, since the civil war.)
“Unless we exterminate rodents, [the plague] is always going to be around,” Epstein argues.
Image copyrightReutersImage captionPublic health workers treat the ground in Yosemite National Park to get rid of fleas
On the other hand, scientists at the National Wildlife Health Center have been working with parks to develop oral vaccines to protect black-footed ferrets and prairie dog – prairie dogs seem to prefer peanut butter-flavoured baits, research shows.
An injectable vaccine for black-footed ferrets has also been created. So maybe it will be possible to rid animals of the disease, at least in the most popular national parks.
Generally, research into the disease is in a “vibrant” state, according to Adalja, with scientists trying to improve ways of diagnosing it, and to develop an effective human vaccine.
The reason? The plague has been classified as a “category A bioweapon”, he says. An average of seven cases of plague per year is one thing, but the risk of biological warfare, even if it’s a remote one, is quite another.
A morning caffeine dose is something that so many of us find irresistible, and according to research, foraging bees seek a similar buzz.
Many plants produce caffeine in their nectar, primarily as a naturally bitter deterrent against plant-devouring insects, like caterpillars.
An experiment with artificial nectar has now shown that bees are attracted to and even “drugged” by the compound.
The research is published in the journal Current Biology. Prof Francis Ratnieks from the University of Sussex, a senior member of the research team explained that previous research had shown that caffeine boosted bees’ memories of the location of a flower.
“So people [already] thought it would affect their perception of nectar,” he told BBC News. To find out if this was the case, the research team set up two artificial flowers for bees to feed from – one containing sugary nectar without caffeine, and another with a concentration of the compound similar to that found in many plants. So they could record each individual bee’s behaviour, the team glued tiny identification numbers to the insects’ backs.
‘Akin to drugging’
The bees would return to the caffeinated nectar more quickly – making slightly more foraging trips, but the most striking finding was that caffeine “made the bees dance” much more.
After a visit to the caffeinated nectar, honeybees were much more likely to perform their waggle dance – a series of movements that communicate the location of a nectar source to their nest-mates.
By dancing, explained Prof Ratnieks, “they’re communicating – hey I’ve found some good food”.
“The vast majority of bees don’t waggle dance – they only do it to communicate a particularly good location.”
So the caffeine had an effect on the insects that was “akin to drugging” – causing behave as though the nectar source was of higher quality, and richer in sugar.
“And it’s presumably cheaper for the plant to produce a small amount of caffeine than a large amount more sugar.”
Dr Margaret Couvillon, who led the study, said the “post-exposure” effects on the bees were also very surprising.
“The bees that had been foraging on the caffeine kept revisiting the feeder [for many days] once it was empty,” she told BBC News.
“So the effects of this one three hour experience (of caffeine) lasted for many days.”
Dr Couvillon explained that, while the classic image of pollination was a “warm, mutualistic relationship,” where the pollinator receives a reward from the plant, this showed a conflict.
She said: “We’re showing a way that the plant gets the upper hand on the bee, through an action that’s akin to drugging.”
