Ch 6 Work and Energy. Work in 1 dimension. Work is when a force is applied and an object is displaced If no displacement occurs or no force is applied then no work is done. The definition of work when the force is parallel to the displacement .
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As long as this person does not lift or lower the bag of groceries, he is doing no work on it. The force he exerts has no component in the direction of motion.
Wtotal=W1 + W2 + W3 … = Σ W
Mechanical Energy is the sum of the kinetic and potential energy of an object
Energy was traditionally defined as the ability to do work.
Not all forces can do work, but ME can
ME= KE + PE
The force required to compress or stretch a spring is:
where k is the spring constant, and needs to be measured for each spring.
Negative because it is a restoring force, acting in the opposite direction of displacement
Conservative forces are ones that do not depend on, or are independent, of the path taken. An example is gravity
If the object were to return to the starting point no net work would be done
This is the Law of Conservation of Energy
Power is the rate at which work is done
In the SI system, the units of power are watts:
The difference between walking and running up these stairs is power – the change in gravitational potential energy is the same.