Work By Variable Forces (Springs) Video Lessons

Concept

# Problem: Stretchable ropes are used to safely arrest the fall of rock climbers. Suppose one end of a rope with unstretched length l is anchored to a cliff and a climber of mass m is attached to the other end. When the climber is a height l above the anchor point, he slips and falls under the influence of gravity for a distance 2l, after which the rope becomes taut and stretches a distance exttip{x}{x} as it stops the climber (see the figure). Assume a stretchy rope behaves as a spring with spring constant exttip{k}{k}.Applying the work-energy principle, find x.Assuming exttip{m}{m_0} = 86 kg , exttip{l}{l_0} = 8.6 m and exttip{k}{k_0} = 870 N/m , determine x/l (the fractional stretch of the rope) at the moment the climbers fall has been stopped.Assuming exttip{m}{m_0} = 86 kg , exttip{l}{l_0} = 8.6 m and exttip{k}{k_0} = 870 N/m , determine kx/mg (the force that the rope exerts on the climber compared to his own weight) at the moment the climbers fall has been stopped.

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###### Problem Details

Stretchable ropes are used to safely arrest the fall of rock climbers. Suppose one end of a rope with unstretched length l is anchored to a cliff and a climber of mass m is attached to the other end. When the climber is a height l above the anchor point, he slips and falls under the influence of gravity for a distance 2l, after which the rope becomes taut and stretches a distance as it stops the climber (see the figure). Assume a stretchy rope behaves as a spring with spring constant .

Applying the work-energy principle, find x.

Assuming = 86 kg , = 8.6 m and = 870 N/m , determine x/l (the fractional stretch of the rope) at the moment the climbers fall has been stopped.

Assuming = 86 kg , = 8.6 m and = 870 N/m , determine kx/mg (the force that the rope exerts on the climber compared to his own weight) at the moment the climbers fall has been stopped.