- #36
MatinSAR
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Can you explain how is it negative ?jbriggs444 said:Not if the surface exerting the normal force ##N## is moving.
Can you explain how is it negative ?jbriggs444 said:Not if the surface exerting the normal force ##N## is moving.
The component of the surface's motion in the direction of the normal force is negative. It is moving away from the force it exerts. So the force pair does positive work on the surface and negative work on the ball.MatinSAR said:Can you explain how is it negative ?
For a small time interval, you will need to imagine the displacement of the ball. Does this displacement have a component parallel or antiparallel to the normal force acting on the ball?MatinSAR said:Can you explain how is it negative ?
N is neither perpendicular nor parallel to displacement.TSny said:Does this displacement have a component parallel or antiparallel to the normal force acting on the ball?
But does the displacement of the ball have a component parallel (or antiparallel) with N?MatinSAR said:N is neither perpendicular nor parallel to displacement.
As the object descends and the surface moves to the left, the object tilts slightly downward.
antiparallel ??TSny said:But does the displacement of the ball have a component parallel (or antiparallel) with N?
N and one of the displacement components are in the opposite direction, so the work is negative.TSny said:Yes. Good. So, do you see how N does negative work on the ball?
Yes.MatinSAR said:N and one of the displacement components are in the opposite direction, so the work is negative.
Is it true ??
Your answer was one of the best I have ever received, even better than my professors at university. Thank you for your valuable time.TSny said:Yes.
Thanks a lot.kuruman said:Right. If there is potential energy to consider, then the conserved quantity is mechanical energy which is the sum of kinetic and potential energy of the two-mass system. In other words, the sum of the kinetic energies of the masses plus the potential energy when the mass is at some point on the ramp does not change as the mass descends and the ramp moves to the left.
Thank you for your help.jbriggs444 said:The component of the surface's motion in the direction of the normal force is negative. It is moving away from the force it exerts. So the force pair does positive work on the surface and negative work on the ball.