N3 – Forces from Motion Get a spring General Physics

The Kinematic Chain A particle moves along the x axis according to the equation x = 2.00 + 3.00 t - 1.00 t2 where x is in meters and t is in seconds. At t=3.00 s, find (a) the position of a particle, (b) its velocity, (c) its acceleration. The object that is sliding only, will be moving with a faster velocity at the bottom. The ball is rolling and thus, some energy from the gravitational potential energy changes the translational kinetic energy and the rotational energy. General Physics

Graphical Analysis of Motion v(t) is slope of r(t) graph a(t) is slope of v(t) graph Derivative is slope, so we can link r, v and a graphically as well as mathematically General Physics

Net Force Diagrams Construct a free-body diagram. Copy the force arrows from the diagram in sequence (tip-to-tail). Draw a double-line arrow to show the vector sum. b) Superimpose circle centered on P; divide circumference of circle into an equal number of spaced units; how many units does the angle span General Physics

Qualitative Example Skier going down slope (Fig N3.1) FKF FD FN Fg General Physics

Practice Problem N3B.1 Draw a free-body diagram and a net-force diagram for a moving motorboat whose motor has just run out of gas. D General Physics

Third-Law Pairs When objects A and B interact, the force the interaction exerts on A is equal in magnitude and opposite in direction to the force it exerts of B. Force pairs connected by Newton’s 3rd Law: Each force in the pair must act on a different object. Each must reflect the same interaction. General Physics

Second-Law Pairs Ex: Normal force and weight, when object is at rest. Force pairs connected by Newton’s 2nd Law: Act on the same object Arise from different interactions Act along same axis Are = b/c a=0 along that axis Ex: Normal force and weight, when object is at rest. What if object is accelerating, like box in an elevator?? General Physics

Coupling Forces Compare the forces exerted by the blocks on each other as they move on a table with some friction. Draw free-body diagram for each block. Determine if A block A exerts a greater force B block B exerts a greater force C the forces are equal Solve together with class. Compare to FBD of mtot=mA + mB. Should get C General Physics

Coupling Forces Compare the forces exerted by the blocks on each other as they move on a table with some friction. Draw free-body diagram for each block. Determine if A block A exerts a greater force B block B exerts a greater force C the forces are equal Ditto General Physics

Third Law Pair Activity Equipment Wired force probe Wireless force probe Open Logger Pro Select Connect Interface, Wireless, and select the name of your wireless probe In the top right corner you will see two tabs, one for each probe. Click on each tab and select zero sensor from the calibrate menu. On one of the sensors, select change direction. Connect the hooks on the force probes together and pull and push until the values are different. Record your results. General Physics

Group Problems N3B.4 N3B.6 N3B.9 N3S.2 N3S.5 Unit IV, Worksheet 4 General Physics