Question

A student, starting from rest, slides down a water slide. On the way down, a kinetic frictional force (a nonconservative force) acts on her. The student has a mass of 62.0 kg, and the height of the water slide is 12.4 m. If the kinetic frictional force does -5.72 × 103 J of work, how fast is the student going at the bottom of the slide?

Answer 1

we have,

mass od student

Since the student starts from rest at the top of the slide,

we have initial speed of student at the top of slide

Let,

speed of student at the bottom of the slide

So,

we get the increase in kinetic energy of the student when it slides down from top to bottom of the slide as,

Kinetic energy at the bottom kinetic energy at the bottom

we have,

work done by kinetic frictional force  

that is energy lost due to frictional force

we have,

height of water slide

So the decrease in potential energy of the student when it slides down from top to bottom of the slide is,

As per the energy conservation principle we have,

decrease in potential energy = increase in kinetic energy + energy lost due to frictional force

that is,

Using given   and   and  

so the student is going at the bottom of the slide with speed of

( expressed in three significant figures )