Kennedy and Lilly are in science class. They are asked to prove that some forces are non-contact forces. The girls list five examples of objects exerting a force on each other without touching. Do you
agree with their list? Tell why or why not?
1. Two like magnetic poles repel each other.
2. Putting on a wool sweater can make your hair get static electricity when it rubs against the
sweater.
3. When you bring two negatively charged balloons near each other they push each other away.
4. Magnets stick to a refrigerator.
Number 1 and 3 demonstrate non-contact forces because the magnets or electrically charged objects exert
forces on each other without touching.
3 is the only example of non-contact forces since like charges repel each other.
Number 1 and 4 are non-contact forces since they both use magnets.
All four are good examples of non-contact forces since they all use either magnets or electric charge which are
non-contact forces.

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).

Atruck driver is attempting to deliver some furniture. first, he travels 8 km east, and then he turns around and travels 3 km west. finally, he turns again and travels 13 km to his destination. what is the drivers distance

Which describes an object in projectile motion? check all that apply.a.gravity acts to pull the object downb.the object moves in a straight path.c.the forward velocity of the object is 0 m/s.d.the object’s inertia carries it forward.e.the path of the object is curved.