Posted by **James** on Sunday, February 27, 2011 at 12:29pm.

A 16-kg child sits on a 5-kg sled and slides down a 143-meter, 30-degree slope, to the nearest m/s what is his or her speed at the bottom?

- Physics -
**drwls**, Sunday, February 27, 2011 at 1:07pm
They want you to neglect friction and use conservation of energy. The masses will not affect the result.

g*L*sin30 = V^2/2

L = 143 m

g = 9.81 m/s^2

Solve for V, and round to nearest m/s

The m/s number that you get will correspond to well over 100 miles per hour - a very unsafe value.

There will actually be appreciable friction unless they are on an ice-covered luge run, and using no brakes or foot dragging.

This is a rather unrealistic problem.

- Physics -
**James**, Sunday, February 27, 2011 at 3:21pm
THANKYOU

- Physics -
**James**, Sunday, February 27, 2011 at 3:26pm
Thank you drwls, there is another question that I am not getting really well right now. It is this: Two skaters are in the exact center of a circular frozen pond. Skater 1 pushes skater 2 off with a force of 100 N for 1.4 seconds. If skater 1 has a mass of 30 kg and skater 2 has a mass of 74 kg, what is the relative velocity (v1 - v2) after the push to the nearest hundredth of a m/s? After reaching the other shore, how fast, to the nearest tenth of a m/s, must skater 1 run around the lake to meet skater 2 at the opposite shore?

Thanks

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