1. Forces and Free-body diagrams By Corina Bot

2. A force is a vector quantity (=> has both magnitude and direction). To fully describe the force acting upon an object, you must describe both the magnitude (size or numerical value) and the direction. It is common to represent forces using diagrams in which a force is represented by an arrow. The size of the arrow is reflective of the magnitude of the force and the direction of the arrow reveals the direction which the force is acting. (Such diagrams are known as free-body diagrams) http://www.glenbrook.k12.il.us/GBSSCI/PHYS/Class/newtlaws/u2l2a.html

3. If we push the block harder and harder, the frictional force will increase, until it reaches a maximum (in this case, 2.5N). If we push harder still, (say, 2.6N), the block will start to move, because we're now pushing harder than the frictional force. Frictional Force http://www.glenbrook.k12.il.us/GBSSCI/PHYS/Class/newtlaws/u2l2a.html http://home.clara.net/darvill/enforcemot/friction.htm http://www.ac.wwu.edu/~vawter/PhysicsNet/Topics/Dynamics/Forces/Tension.html http://en.wikipedia.org/wiki/Force Tension Force Spring Force Contact Forces Normal Force Applied Force Frictional Force Tension Force Spring Force Normal Force Gravitational Force

4. Action-at-a-Distance Forces Gravitational Force Electrical Force Magnetic Force Iron filings and compasses show the shape and direction of the magnetic field http://en.wikipedia.org/wiki/Force http://en.wikipedia.org/wiki/File:EfieldTwoOppositePointCharges.svg http://www.school-for-champions.com/science/magnetic_detection.htm Electric vector field surrounding two opposite point charges. Red is positive, green is negative. An initially stationary object - allowed to fall freely under gravity drops a distance which is proportional to the square of the elapsed time. Gravitational Force

5. x y 0 A mini-car is pulling a block, with a force of 190N, as shown in figure. The block has a mass of 15 kg and the coefficient of kinetic friction between the bottom of the block and the surface is 0.6. Find the acceleration of the cart. F app =190 N m = 15 kg    a x = ? 15 kg By definition:

6. From equation (1): From equation (2): From equation (3): F app =190 N m = 15 kg    a x = ? x y 0

7. A descendant of the original apple tree can be seen growing outside the main gate of Trinity College, Cambridge, UK, below the room Newton lived in when he studied there.