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my question is, when using energy conservation when do i put the potential energy of gravity negative? if its under where it set my potential energy to 0? or am i wrong, is gravity's potential energy always positive (except at my set u=0 point) ?

can someone explain this to me, having trouble getting ANYthing done because i do not understand how to set up these homework questionsfor example, this is a ball pushed into a barrel, compressing the spring, ball has initial velocity 0

here are the values,

k = 667 N/m

mass of ball = 1.5kg

ball is pushed into tube .25 meters

if u=0 is set at the mouth of the barrel, then the initial potential energy is mgh+.5kx^2?

or is it -mgh+.5kx^2? -mgh-.5kx^2?

can someone explain this to me, having trouble getting ANYthing done because i do not understand how to set up these homework questionsfor example, this is a ball pushed into a barrel, compressing the spring, ball has initial velocity 0

here are the values,

k = 667 N/m

mass of ball = 1.5kg

ball is pushed into tube .25 meters

if u=0 is set at the mouth of the barrel, then the initial potential energy is mgh+.5kx^2?

or is it -mgh+.5kx^2? -mgh-.5kx^2?

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