Machines and engineering

29 to explore

• Watch Try it What If? Lab What if a beam stood on its edge? The same steel beam can lie flat or stand on its edge. It weighs exactly the same either way, yet in our model the tall way sags only a quarter as much under a truck. Find out why a beam's height matters far more than its width.
• Watch Try it What If? Lab What if a boat carried too much cargo? A steel boat floats because its hollow shape pushes aside lots of water. Every kilogram of cargo pushes it a little deeper. Load Olly's model boat step by step, find the most it can carry, then see what happens with 400 kilograms on board.
• Watch Try it What If? Lab What if a boat changed shape? Drop a solid block of steel in water and it sinks straight down. Shape steel into a hollow boat hull and it floats. In our model, a steel hull the same outside size as the block bobs on the water with about a third of it showing, and can even carry cargo. Find out how shape, not just material, decides whether something floats.
• Watch Try it What If? Lab What if a bridge weighed nothing? A long bridge carries more than traffic: it also has to hold up its own heavy body. In Olly's model, switch off a 60-meter steel beam's weight and see how much of its strength was being used just to hold itself up.
• Watch Try it What If? Lab What if a bridge were built with different materials? Steel, wood and aluminum all behave differently when a heavy truck rolls onto them. In our model, a wooden beam the same size as a steel one bends about five times as much under the same truck, yet it still holds, partly because wood is so much lighter. Find out why bending and breaking are two different things.
• Watch Try it What If? Lab What if a bridge were held up at one end only? A beam held at only one end, like a diving board, is called a cantilever. In this lab a 10-meter steel beam carries a 20-tonne truck. Take away one support and watch how much more it bends, and find where the beam works hardest.
• Watch Try it What If? Lab What if a bridge were twice as long? A steel beam bridge 20 meters long sags about 14 millimeters under a 20-tonne truck. Make it twice as long and the sag does not just double: in our model it grows almost 14 times. Find out why long bridges need different designs.
• Watch Try it What If? Lab What if a crane used more pulleys? Lifting a 100-kilogram crate straight up on one rope is hard work. In this lab, add pulleys so that more pieces of rope hold the load. Watch how the pull you need gets smaller, and how much more rope you have to pull.
• Watch Try it What If? Lab What if a glider had short, stubby wings? A glider flies with no engine, so it needs wings that work as well as possible. Squash a glider's long, thin wings into short, stubby ones with the same area, and see what happens to its lift in Olly's model.
• Watch Try it What If? Lab What if a house had no insulation? Heat always leaks out of a warm house into the cold outside. Insulation in the walls and roof slows that leak down. In our model, an insulated house on a freezing day needs its heater only about a third of the time. Take the insulation away and the same heater runs nonstop, and the house still cools to about 17 °C.
• Watch Try it What If? Lab What if a house were built on soft clay? A building presses down on the ground under its foundation. Sand, gravel and rock can each safely carry a different amount. In this lab, a 300-tonne building stands safely on sand. Move it onto soft clay without changing anything else, and see what happens and how to fix it.
• Watch Try it What If? Lab What if a plane had different wings? A plane's wings push air down, and the air pushes the wings up. That push is called lift. In our model, a small plane cruising at 60 meters per second has plenty of lift. Cut its wing area about in half and the lift drops by about half too, not enough to hold the plane up, unless it flies much faster.
• Watch What If? Lab What if a robot had only one sensor? A sensor is a part that lets a robot notice something: light, a bump, a sound. Most robots use several kinds. In this thought experiment, imagine a robot with only a camera, and then one with only touch. What might each one miss? Then see how NASA's Perseverance rover combines many cameras and other sensors to explore Mars.
• Watch Try it What If? Lab What if a roller coaster had greater friction? Once a roller coaster is let go at the top of its first big hill, gravity does the rest: all its energy comes from that hill. Friction from the wheels and the air slowly uses that energy up. In our model, a coaster with smooth wheels finishes the whole ride. Make the friction four times bigger and it slows down so much that it can't get over the second hill and rolls back.
• Watch Try it What If? Lab What if a roller coaster were launched? A roller coaster gets its energy from height, but some get it from a fast launch instead. In this lab, a car on a small 15-meter hill can't make a loop. Give it a 10-meter-per-second launch and see if that extra speed carries it all the way around.
• Watch Try it What If? Lab What if a roller-coaster loop were bigger? A coaster car needs enough speed at the top of a loop to stay pressed against the track. In this lab, the car starts at 40 meters and easily makes a 10-meter loop. Double the loop to 20 meters and see what happens, then find how tall the first hill must be.
• Watch Try it What If? Lab What if a wind turbine had different blades? A wind turbine's blades sweep out a big circle, catching the wind that blows through it. Make the blades twice as long and the circle holds four times as much wind. In our model, that turns about 1.2 megawatts of electricity into about 4.9 megawatts, in the same wind. Find out why wind turbines keep getting bigger.
• Watch What If? Lab What if bridges could float? Most bridges rest on piers that reach down to solid ground. But some bridges really float, held up by huge hollow concrete boxes called pontoons. Find out why engineers float a bridge, how heavy concrete can float at all, and what wind and waves do to a road on the water.
• Watch Try it What If? Lab What if buildings had different foundations? A building's whole weight presses down through its foundation onto the ground. A wide foundation spreads that weight out, like snowshoes on snow. In our model, a 200-tonne building on sand is safe on a 40-square-meter footing. Shrink the footing to 8 square meters and it presses five times harder, more than the sand can take, so the building would sink and could crack or tilt.
• Watch What If? Lab What if canals had no locks? Canals let boats cross land, but land goes up and down while water wants to stay level. Locks solve this: they are like water-filled stairs that lift and lower boats one step at a time. Explore how locks work, what a canal without them can and cannot do, and the giant locks of the Panama Canal.
• Watch What If? Lab What if cities had no traffic lights? Traffic lights share a busy crossing by giving each direction a turn. In this thought experiment, imagine a city without them. Would drivers take turns by the rules of the road, would roundabouts do the job, or could smarter signals help?
• Watch What If? Lab What if elevators did not exist? Elevators carry people up tall buildings in seconds. But before safe elevators, most buildings were only a few floors high. Imagine a world without them: shorter buildings, many more stairs and cities that spread out instead of up.
• Watch Try it What If? Lab What if pulleys had friction? A pulley system with four ropes can make a heavy crate feel four times lighter, but only in a perfect world with no friction. Turn friction up in Olly's model and see how much harder you have to pull, and where the extra work goes.
• Watch What If? Lab What if skyscrapers could not sway? Tall buildings sway a little in strong winds and earthquakes, and some even hang giant weights inside to calm the motion. Imagine a skyscraper that couldn't sway at all, and follow the clues: the push of the wind, giant swinging weights, and bending without breaking.
• Watch Try it What If? Lab What if solar panels received less sunlight? A solar panel turns sunlight into electricity, so the more sunshine reaches it, the more power it makes. In our model, one rooftop panel on a clear summer day makes about 310 watts at noon. When clouds let through only a quarter of the direct sunshine, it makes only a quarter as much. Then find out why real panels can do better than our model on cloudy days.
• Watch What If? Lab What if there were no gears? A gear is a toothed wheel that turns another one. Gears can make things turn faster or slower, and trade speed for turning force. In this thought experiment, imagine bikes, clocks and machines with no gears, then see what the very first pedal bikes and old clocks tell us.
• Watch What If? Lab What if there were no wheels? A wheel turning on an axle makes heavy loads much easier to move. But people moved big things long before wheels, using sledges and rollers. In this thought experiment, see how they did it, when the first wheels appeared, and what a day without wheels might be like.
• Watch What If? Lab What if tunnels could be dug anywhere? Tunnels carry trains, cars and water through mountains and under rivers. But digging one is hard: the ground can be solid rock or soft mud, and water is always trying to get in. Explore how tunnel builders hold back rock and water, and how giant boring machines dig and line a tunnel as they go.
• Watch Try it What If? Lab What if you could lift a car with a lever? A lever is a bar that turns on a pivot called a fulcrum. In this lab, a 1,000-kilogram load sits on a lever. Move the fulcrum close to the load, make your side long, and see how small your push becomes, and how far your end has to move.