Grip, gravity and the physics of a good catch.

Friction is the sideways force that stops your shoe or fingers sliding. In the simple model every physics class uses, the most friction you can get is F ≤ μ × N: the friction coefficient μ (how grippy the two surfaces are together) times the normal force N (how hard you press into the rock). On a slab tilted at angle α, gravity tries to slide you down the slope with a force mg sin α while pressing you in with mg cos α. You only stay put if μ ≥ tan α.

What helps grip

• Weight over your feet: leaning into a slab feels safer but reduces the push into the rock, so your feet skate. Hips out, heels down.
• Chalk: magnesium carbonate dries sweat from your fingers. Brush excess chalk off holds; caked chalk gets slippery.
• Conditions: cool, dry air beats heat and humidity. Climbers at Badami start very early, even in January, because direct sun makes rock and rubber greasy.
• Rock type: Hampi's granite and Badami's sandstone feel completely different: rough crystals versus a finer, sometimes softer surface. Wet sandstone can be weakened, so let it dry after rain.

On a vertical wall, your weight acts at your centre of mass, roughly at your hips. If your hips are a distance d out from the wall, gravity creates a torque (turning effect) of m g × d that tries to topple you backwards around your feet. Your hands, roughly a height h above your feet, must pull in with a force that cancels it: F_arms ≈ m g × d ÷ h.

Moves that use the physics

• Straight arms: hanging from straight arms lets bones and ligaments take the load while muscles partly recover.
• Legs push, arms steer: leg muscles are far bigger than forearm muscles. Stand up on your feet; don't pull up on your arms.
• Drop-knee and flagging: turning a hip into the wall or pushing a leg out sideways moves your centre of mass under the hold, so you don't "barn-door" (swing open like a door).
• Overhangs: keep tension through your core and toes so your feet stay on. If they cut loose, your arms suddenly carry your whole weight.

A falling climber has kinetic energy that the rope must absorb by stretching. A dynamic climbing rope is designed to stretch, so it stops you over a longer distance with a lower peak force. The key number is the fall factor: f = fall distance ÷ rope length paid out. A 3.5 m fall on 10 m of rope (f = 0.35) is far gentler than a 3.5 m fall on 2.5 m of rope near the belay (f = 1.4), because there's four times less rope to stretch.

Treating the rope as an ideal spring of stiffness EA gives the peak force F = m g (1 + √(1 + 2 f EA ÷ m g)). Notice that the length of the fall on its own isn't in the formula: only the fall factor is.

The standard drop test

The UIAA's rope standard (UIAA 101, which requires the European norm EN 892) drops a test mass, 80 kg for single and twin ropes and 55 kg for half ropes, in a severe factor-1.77 fall onto a fixed metal edge. A single rope must hold the first drop with a peak force of no more than 12 kN (8 kN for a half rope, 12 kN for a twin pair), survive at least 5 drops (12 for twins), and stretch no more than 40% during the fall. Rope maker Petzl points out that real falls are usually softer than the test, because the belayer moves, the rope slips through the device and your harness and body flex.

When a sling or rope shares a load F between two anchor points, each leg carries F ÷ (2 cos(θ/2)), where θ is the angle between the legs. Narrow angles share the load nicely. Wide angles multiply it.

Why the top bolt sees more than you

In a lead fall, the rope runs from you, up through the top quickdraw, and back down to the belayer. The bolt holds both strands: your side and the belayer's side (a bit less, because of friction over the carabiner). That's why it can see well over your own peak force; the Fall Lab uses an illustrative 1.6 ×.

Sport versus trad

• Sport climbing: you clip pre-placed bolts. At Badami, local climbers report that some bottom bolts have been stolen or chopped, so a stick clip (a pole for clipping the first bolt from the ground) is recommended.
• Trad climbing: you place removable protection, such as nuts wedged into constrictions and spring-loaded cams. A cam turns your pull into outward pressure on the crack walls; friction holds it. It needs solid rock and the right crack shape.
• Strength markings: certified carabiners and slings are marked with their rated strength in kN. Even so, rock quality is often the weak link.

Bouldering means short, hard climbs close to the ground, protected by crash pads and spotters instead of a rope. Falling from height h, you hit the ground at v = √(2 g h). To stop, you need an average deceleration of a = v² ÷ (2 d), where d is your stopping distance: the pad's compression plus how much your knees bend.

Landing well

• Feet first, knees soft, then roll back onto your bottom and back. Don't put your arms out straight to catch yourself: wrists break.
• Pads cover the landing, not the rock: place them where you'll actually fall, and close gaps between pads. Hampi's boulders often have uneven, rocky landings.
• Spotters steer, they don't catch: hands up near your hips and back, guiding you onto the pad and protecting your head.
• Down-climb or jump on purpose: a controlled drop beats a surprise fall.

Lifting your body up a route takes mechanical work W = m g h. Your body burns several times more than that, because muscles are inefficient and much of climbing is gripping and holding still, which costs energy without lifting you at all.

The pump

Squeezing a hold hard and continuously compresses the blood vessels inside your forearm muscles. Less oxygen gets in and waste products build up; the muscles swell and your grip fades. The fixes are mostly technique: climb smoothly, rest on big holds with straight arms, shake out each arm in turn, and grip only as hard as you need.

Fingers need time

Tendons and the finger "pulleys" that hold them adapt much more slowly than muscles. Sharp pain in a finger during a hard crimp is a reason to stop. Warm up on easy climbs, build up volume gradually, and get finger injuries checked by a professional.