How can the human body stick to a sheer cliff?
What techniques do climbers use to help them get up a cliff face? What forces are at work in rock climbing?
David travels to Oregon to
learn about the physics and
biomechanics of rock climbing.
Although rock climbing does not draw large crowds, it claims an annual growth rate of 50%, with women accounting for one-quarter of all climbers. Before beginning, however, climbers should get professional instruction so they understand how to use ropes to protect themselves against the forces of gravity.
Climbers choose nylon ropes because they stretch and absorb the shock of a fall. Good climbing ropes will stretch to double their original length before breaking and have a breaking strength of over three tons of force. Ropes are used in two ways. In "top roping" (the safest method), climbers fix webbing to an immovable object at the top of a cliff--usually a tree or a rock. They attach the webbing to a carabiner. Then they pass a rope through the carabiner, letting the two ends dangle down the side of the cliff. One end is tied to the climber. The other is tied to and held by a person at the bottom, who keeps the rope taut to stop a fall.
Sometimes top roping is impossible because the climb is longer than one-half a rope length or because the climbers don't have access to the top of the cliff to fix the webbing. In that case, someone must "lead climb" and place protection in the cracks in the rock. The rope is clipped into the protection. The second climber belays the lead climber.
Biomechanics are crucial to climbing. Bones, joints, and muscles combine to provide wedges and levers--all the simple tools necessary to make it to the top. The most sophisticated climbing "gadget" is the human hand. Hand jams allow climbers to grab holds in seemingly impossible places. Climbers also manipulate their center of mass by working their bodies away from the rock face. This puts more force onto their feet. High-tech climbing shoes make good use of that force. Their rubber soles conform to the surface of the rock and create enough friction (or stickiness) to hold on to steep angles.
Climbing techniques put a variety of forces to work. In "face climbing," the most common technique, climbers pull down on handholds and push up on footholds to advance up the rock. By keeping their weight balanced over their feet, the climbers remain stable. In "stemming," climbers push their legs outward against the two opposing rock faces. Their outward push forces their shoes into the walls and the shoes generate an upward frictional force which opposes gravity and allows the climbers to ascend.
Climbing is basically applied physics. Grace, rhythm, balance, concentration, and flexibility count more than strength. Although incorrect techniques, bad weather, and misuse of equipment can produce some dangerous situations, climbing is a safe sport when proper procedures are followed.
Additional sources of information
Create some friction by moving one object against another.
Friction is the force that causes resistance when we try to slide one surface over another. Friction helps us walk, run, and jump. Without it, a climber would have a very difficult time going up a steep slope.
Materials
Questions
Climbers climb on different types of rock: quartzite, limestone, sandstone, granite. How do these rock formations differ? How might that affect climbing techniques? Find some exposed bedrock near your house. Examine the rocks and holes.
To help you understand a belay, wrap a medium thick rope (over 1/4" thick) two times around a flagpole and have a one-way tug of war. One person should try to pull the rope with both hands while the other person holds the rope with one finger. The friction of the cord wrapped around the flagpole acts as a belay. The belay increases the force exerted by one finger so much that the person pulling on the rope with both hands is unlikely to be able to pull much rope at all. This is how a belayer can counteract the large forces generated in a rock climbing fall.
Climbers are constantly exposed to the elements and must devise their own protection. What does this involve? Focus on different types of adaptation, such as clothing, bedding, and sun protection.
Some mountaineering or outdoor stores have rock walls and many cities are acquiring rock gyms. Find out whether there are any climbing areas near you and take a field trip to learn more about rock climbing principles.
The human hand is our prime manipulative tool. It has an opposable thumb, which gives us a great deal of dexterity. Think of the ways you use your hands as tools. Tape one of your thumbs to the side of your hand to immobilize it. You'll soon understand why the thumb makes your hand such an effective tool.
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