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 .
Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.
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.
Work done by forces that oppose the direction of motion, such as friction, will be negative.
The work done may be positive, zero, or negative, depending on the angle between the force and the displacement
If there is more than one force acting on an object, we on the angle between the force and the can find the work done by each force, and also the work done by the net force
Wtotal=W1 + W2 + W3 … = Σ W
6-3 & 6-4 KE, PE and Work Energy Principle on the angle between the force and the
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
Potential energy can also be stored in on the angle between the force and the certain materials when they are compressed; the figure below shows potential energy yielding kinetic energy.
Hooke’s Law on the angle between the force and the
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
6-5 on the angle between the force and the Conservative and Nonconservative Forces
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
6-6 forces. Mechanical Energy and Its Conservation
Total forces. mechanical energy ME= KE + PE therefore
This is the Law of Conservation of Energy
6-10 Power forces.
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.