91热爆

You will need:

• long ruler
• Poster tube
• sock
• Rice or lentils
• A bat or racket of any kind
• A willing helper

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When you鈥檙e travelling you need to be able to react fast if something unexpected happens. Here are two ways to test how quick 鈥� or slow - your reaction time is.

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The first method is very simple. All you need is a long ruler, and another person to help.
Sit or stand with your forearm and elbow resting on a table, so that your wrist hangs over the edge. Ask your helper to hold the ruler vertically, with the highest numbers at the top. It needs to hang down between, but not touching, your thumb and fingers, with the 0 mark level with your fingers.听 Then, ask your friend to suddenly drop the ruler without telling you exactly when they鈥檙e going to do it. When it falls鈥� you need to catch it! Measure how many centimetres it has fallen through your hand. If you look on the internet you can find charts which will show you how the distance the ruler has fallen equates to your reaction time in seconds. What happens to your reaction time as you repeat the activity?

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The second method is a game called Splat the Rat.听 This one needs a lot of room, so it鈥檚 best to do it outside. Again, you鈥檒l need a willing assistant. You also need a poster tube, a racquet or bat of some kind (for the splatting), and something to act as your 鈥渞at鈥�. Dick and Dom used a sock stuffed with a sandwich bag full of rice, but you could use a beanbag or a small soft toy. Your rat needs to be small enough to slide down your tube without getting stuck.
Ask your helper to hold the poster tube up vertically, and to look after your 鈥渞at鈥�. You鈥檒l be aiming to whack the rat when it pops out of the bottom of the tube 鈥� so make sure your helper holds the tube at a slight angle and as far as from their body as possible to avoid getting splatted themselves!听 You may need two people to help if you have a large tube.

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Get yourself ready, with the bat. Then ask your helper to drop the rat down the tube.听 Can you hit it with the bat?

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Your reaction times are not as fast if you are distracted. You can try this for yourself. What happens if your helpers make a lot of noise when you鈥檙e trying to splat the rat?

Friction is a force between two surfaces that are touching each other. It can act to slow moving things down 鈥� but it can also be important for keeping vehicles moving and under control. A car's tyres are not completely smooth; they are also grippy 鈥� you want the wheels to turn, not to skid. In bad weather, when the roads are wet or icy, there is less friction, and the risk of wheels sliding increases.

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You can see the effect of friction for yourself by having a tug of war. You need a rope, or a rolled up pillowcase or tea-towel; and a friend.听 You also need a smooth floor, and lots of space; don鈥檛 do this anywhere you might knock something over!听 One of you needs to stand barefoot, and the other person should wear just their socks. Who do you think will win the tug of war?听 The person in the socks is experiencing much less friction between the floor and their feet 鈥� so if you want to win, make sure you鈥檙e the one going barefoot!

You will need:

• Something to act as a car 鈥� eg. a roller skate
• Eggs
• Eggboxes
• Bubble wrap
• Balloons
• Sticky tape
• Sponges

Car manufacturers spend a lot of money on crash test equipment, but you can follow in Dick and Dom鈥檚 footsteps and make your own. They used roller skates in place of cars, and eggs in place of passengers. They also had some bits of egg boxes to act as seats, and a selection of things like bubble wrap, sponges, scraps of material and balloons to help protect their eggs.听听 They drove their skates down a slide, with a tea tray at the bottom set up as a barrier 鈥� but you can improvise with whatever you have to hand.

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Your challenge is to use the materials you have to protect your eggs in a crash. Think about the real safety measures used in cars. How might you replicate a seat belt, or an airbag? Can you make your eggs so safe that they won鈥檛 crack?

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What鈥檚 happening? When a car stops suddenly, the people inside keep moving. So some safety equipment, such as a seatbelt, is designed to slow and halt that movement, to keep you inside the car. It鈥檚 also better for the car to take the impact of a crash, and have the forces disperse through the car itself, rather than through the passengers inside.听 The safety measures you create for your egg are doing exactly the same thing.