Sunday

December 21, 2014

December 21, 2014

Posted by **julia** on Wednesday, December 5, 2007 at 1:16pm.

- physics -
**Damon**, Wednesday, December 5, 2007 at 4:07pmThere are two ways of doing this problem, the energy way and the work way.

The energy way is to say the potential energy lost by moving down is the kinetic energy gained at the bottom.

Potential energy lost = m g times the change in height

The change in height is from:

sin (30) = change in height / 4

so change in height = 4 sin 30 = 2 meters down

so the potential energy lost is:

m * 9.8 * 2 which is 19.6 m Joules

That 19.6 m Joules is the kinetic energy at the bottom

KE = 19.6 m

since m = 20 kg

KE = 20*19.6 = 392 Joules

NOW the other way

The work done is the force down the ramp times the distance run

The component of force down the ramp is

m g cos 60 = 20 *9.8 * .5 = 98 Newtons

That 98 newtons pushes a distance of 4 meters so the work done is

98 * 4 = 392 Joules

That work done is used to increase the kinetic energy of the child so the kinetic energy is also 392 Joules.

**Answer this Question**

**Related Questions**

Physics - A 37 kg child roller skates, initially at rest, rolls 2.0 m down an ...

Physics - A 37 kg child roller skates, initially at rest, rolls 2.0 m down an ...

Physics - A 37 kg child roller skates, initially at rest, rolls 2.0 m down an ...

Physics - A 16kg child on roller skates rolls 2m down an incline at 20 degrees ...

Physics Energy and Work - A 20.0 kg child on skis, initially at rest, slides 2.0...

Physics - A solid sphere rolls without slipping from rest down a plane at 4.00m ...

Physics - A 2000kg car begins from rest and rolls 50.0m down a frictionless 10 ...

Physics - 15. [1pt] A thin hoop of radius r = 0.59 m and mass M = 9.2 kg rolls ...

Physics - forces acting at an angle - The physics of tobogganing and forces at ...

physics - A large 22 cm marble rolls from rest down an incline. Its center has a...