- #1
silentsaber
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Homework Statement
1.)A mass is on a frictionless horizontal surface and attached to a horizontal spring of
spring constant 200 N/m. If the mass is released from rest when the spring is
compressed by 10 cm, what will its kinetic energy be when the spring is stretched by
7 cm?
2)A child on a sled starts at the top of a 1.6 m high hill and slides along a straight
incline to the bottom at a constant velocity. If the mass of the child and sled is 40 kg,
what is the work done by friction during his slide down the hill?
Homework Equations
1.) 1/2mv^2=1/2KX^2
2.) W=1/2mvf^2-1/2mvi^2 or W=FD
The Attempt at a Solution
for the first one i tried plugging in the numbers to 1/2mv^2=1/2Kx^2 and tried to ifnd the kinetic energy that way but it didnt work what went wrong?
The second one i tired using the work energy theorem but but it said constant velocity so that woould cuase the both teh final velocity and initil velocity to be the same and since the mass is the same wouldn't the W be 0? i also tried listing the forces out but then since it doens have an angle i got stuck... what did i do wrong i am confused