Why a body floats and how to start swimming
Water pushes up on anything placed in it. This push is called buoyancy. Air in your lungs makes your body lighter, so most people float if they lie flat and stay calm.
To start: breathe in, lie flat on your front, look down, keep your hips high, and kick from the hips with straight, loose legs. A flat body moves through water more easily than a tilted one.
The four swimming strokes
Freestyle (front crawl): face down, arms go round one after the other, legs kick up and down. It is the fastest stroke.
Backstroke: face up, arms go round one after the other, legs kick. You breathe easily because your face is out of the water.
Breaststroke: face down, both arms open out and come back together, legs kick like a frog. It is slower but good for beginners.
Butterfly: both arms go round together over the water, and the body moves in a wave with a dolphin kick. It needs strength.
In a medley race, swimmers use all four strokes one after another.
Breathing, turns and starts
Breathe out slowly into the water, and breathe in quickly when your mouth is above the surface. At the end of the pool you turn and push off the wall with your feet. A race starts with a dive from a block. The streamlined shape (arms stretched, head between them) glides farthest.
Water safety rules
- Never swim alone. Swim where an adult or lifeguard can see you.
- Look at the depth before you enter. Do not dive into shallow or unknown water.
- Do not swim in rivers or the sea when the current is strong.
- If a person is in trouble, shout for help, then reach with a pole or throw a rope, tube or bottle. Do not jump in yourself, because a frightened person may pull you under.
- If you get tired, roll on your back and float, then wave and call.
Skating and skiing on ice and snow
Friction is the force that slows things that slide. A thin skate blade or a ski on ice or snow has very little friction, so you glide. A thin layer of water or smooth snow helps the sliding.
To move: push sideways and backward with one foot, then glide on the other. Bend your knees to keep balance. To stop on skates, turn the blades across the direction of motion; on skis, point the tips together in a wedge. Wear a helmet, and learn to fall sideways and relax.
Key formulas and definitions
- Key terms: buoyancy = upward push of water
- Key terms: friction = force that slows sliding; low on ice and snow
- Four strokes: freestyle, backstroke, breaststroke, butterfly
- Water rescue: shout, reach, throw, do not go in
- Speed = distance / time (for example 50 m in 25 s = 2 m/s)
Worked examples
1. A swimmer swims 50 m in 25 seconds. What is the speed?
Speed = 50 / 25 = 2 m/s.
2. Name the stroke where both arms move together and the legs kick like a frog.
Breaststroke.
3. A child is struggling 5 m from the pool edge. What should you do?
Shout for the lifeguard, then reach with a pole or throw a float. Do not jump in.
4. Why does a skater glide farther on ice than on a wooden floor?
Ice gives very little friction, so there is almost nothing to slow the skater down.
Common mistakes
- Lifting the head high while swimming. This sinks the hips and makes you slower.
- Holding the breath all the time. Breathe out into the water and breathe in at the surface.
- Jumping in to save a friend. Reach or throw from the edge first.
- Thinking breaststroke is the fastest. Freestyle is the fastest stroke.