Question

A girl is sitting on a sled. She is pushed by a spring that was compressed 0.8m. The spring constant is 2500 N/m. After moving 2.5 m across a surface that applies 60 n of friction, the girl and the sled slid up a frictionless hill. How high do the girl and the sled rise up by the time they stop?

Answer 1

spring energy = 1/2 k x^2 = 1/2 * 2500 * 0.8^2 ... Joules

friction work = f * d = 60 * 2.5 ... Joules

hill height = [(spring energy) - (friction work)] / (m * g)
... you need the girl/sled mass

Answer 2

the girl/sled mass is 27kg

Answer 3

Fs = 2500N/m * 0.8m = 2000 N.
Fs-Ff = M*a
2000-60 = 27a
a = 71.9 m/s^2.

V^2 = Vo^2 + 2a*d = 0 + 143.8*2.5 = 359.5
V = 19 m/s.

V^2 = Vo^2 + 2g*h = 0
19^2 + (-19.6)h = 0
h = 18.4 m.