Answer:
Energy was lost as frictional energy. Hence when trying to move up to the top for the second time, the skateboarder was unable to do so.
The others provided additional energy to make up for the lost energy by dending their knees
Explanation:
According to law of conservation of energy, energy can niether be created nor destroyed but can change its form.
Here kinetic energy of skate boarder was converted into frictional energy and lost in the surroundings(energy was not destroyed but simply changed its form to energy of particles in the air). She was therefore unable to reach to the top the second time.
Other skateboarders faced the same, but the added energy to their movement by converting energy stored in their bodies to their kinetic energies. They were therefore abole to reach to the top.