Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Photoelectric effect wikipedia , lookup
Compact Muon Solenoid wikipedia , lookup
Renormalization wikipedia , lookup
Eigenstate thermalization hypothesis wikipedia , lookup
Noether's theorem wikipedia , lookup
Scalar field theory wikipedia , lookup
Theoretical and experimental justification for the Schrödinger equation wikipedia , lookup
Electron scattering wikipedia , lookup
Renormalization group wikipedia , lookup
Kinetic Energy Physics 1D03 - Lecture 19 Kinetic Energy Definition: for a particle moving with speed v, the kinetic energy is K = ½ mv2 (a SCALAR quantity) Then the Work-Energy Theorem says: The total work done by all external forces acting on a particle is equal to the increase in its kinetic energy. W = ΔK = Kf – Ki Physics 1D03 - Lecture 19 • Kinetic Energy is measured in joules (1J=1N·m). • Kinetic energy is a scalar; the work-energy theorem is a scalar relation. • This theorem is equivalent to Newton’s Second Law. In principle, either method can be used for any problem in particle dynamics. Physics 1D03 - Lecture 19 How to deal with friction If there is friction in the system, then: ΔK=Wf = -ffd Since ΔK = Kf - Ki = -ffd Therefore Kf = Ki - ffd Physics 1D03 - Lecture 19 Example 1 A bartender slides a 1-kg glass 3 m along the bar to a customer. The glass is moving at 4 m/s when the bartender lets go, and at 2 m/s when the customer catches it. Find the work done by friction, and calculate the force of friction. Physics 1D03 - Lecture 19 Example 2 A 6.0 kg block initially at rest is pulled to the right for 3.0m with a force of 12N over a surface. Determine its final velocity if: a) the surface has no friction b) the surface has a coefficient of kinetic friction of 0.15 How else could we solve this problem ???? Try it !!! Physics 1D03 - Lecture 19 Example 3 A block of mass 1.6kg resting on a frictionless surface is attached to a horizontal spring with a spring constant k=1.0x103 N/m. The spring is compressed to 2.0cm and released from rest. a) Calculate the speed of the block as it passes the x=0 point. b) Calculate the block’s speed at the x=1.0 cm point. c) Calculate the block’s speed at the x=0cm point if there is a constant frictional force of 4.0 N. Physics 1D03 - Lecture 19