For our first example of motion in a plane, suppose you are operating a radio-controlled model car on a vacant tennis court. The surface of the court represents the x-y plane, and you place the origin at your own location. At time t1=2.0s the car has x and y coordinates (4.0 m, 2.0 m), and at time t2=3.1s it has coordinates (7.0 m, 6.0 m). For the time interval from t1 to t2, find (a) the components of the average velocity of the car and (b) the magnitude and direction of the average velocity.

1) Suppose you reverse the car’s motion, so that it retraces its path in the opposite direction in the same time. Find the x-component of the average velocity of the car.

2) Find the y-component of the average velocity of the car.

3) Find the magnitude of the average velocity.

4) Find the direction of the average velocity.

Part f - example: finding two forces (part i) two dimensional dynamics often involves solving for two unknown quantities in two separate equations describing the total force. the block in (figure 1) has a mass m=10kg and is being pulled by a force f on a table with coefficient of static friction îľs=0.3. four forces act on it: the applied force f (directed î¸=30â above the horizontal). the force of gravity fg=mg (directly down, where g=9.8m/s2). the normal force n (directly up). the force of static friction fs (directly left, opposing any potential motion). if we want to find the size of the force necessary to just barely overcome static friction (in which case fs=îľsn), we use the condition that the sum of the forces in both directions must be 0. using some basic trigonometry, we can write this condition out for the forces in both the horizontal and vertical directions, respectively, as: fcosî¸â’îľsn=0 fsinî¸+nâ’mg=0 in order to find the magnitude of force f, we have to solve a system of two equations with both f and the normal force n unknown. use the methods we have learned to find an expression for f in terms of m, g, î¸, and îľs (no n).

As you are trying to move a heavy box of mass m, you realize that it is too heavy for you to lift by yourself. there is no one around to , so you attach an ideal pulley to the box and a massless rope to the ceiling, which you wrap around the pulley. you pull up on the rope to lift the box. use g for the magnitude of the acceleration due to gravity and neglect friction forces. once you have pulled hard enough to start the box moving upward, what is the magnitude f of the upward force you must apply to the rope to start raising the box with constant velocity? express the magnitude of the force in terms of m, the mass of the box.

Apersons beliefs and general outlook, which act like filters on the information they receive are called ?