# General Physics Q&A's

Topics: Newton's laws of motion, Force, Mass Pages: 5 (1817 words) Published: September 29, 2013
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Textbook Sections that I read: 2.1-3
Important Concepts:
An interaction between two objects can be described and measured in terms of two forces. The force is a push or either a pull. There are two types of forces. #1 is a long range force and this force does not require the objects involved to be touching each other. An example of this is when you are holding a magnet away from a refrigerator and you are able to feel the magnetic pull. #2 is a contact force and this occurs only when the objects are touching one another. A vector in physics is another name for a force. All vectors have a direction in space and magnitude as well. Both direction and magnitude are of equal importance. Any vector can be expressed as the sum of vectors that are parallel to the x-, y- axes (if needed the z-axes as well). These components indicate the magnitude and direction of the three vectors along the axes. Reading Assignment questions:

8. (a) Is it possible for the sum of two vectors to be smaller in magnitude than the magnitude of either vector? Yes it is possible if the scalar product of the two vectors is negative. (b) Is it possible for the magnitude of the sum of two vectors to be larger than the sum of the magnitudes of the vectors? It isn’t possible because the sums would only be able to be equal at best. 18. (a) If two vectors have the same magnitude, are they necessarily equal? If not, why not? It depends on the direction they are in. They could be unequal if they are in different directions. Can two vectors with different magnitudes be equal? It would not be possible for them to be equal.

Reading Assignment #2: Newton’s First Law
Textbook sections that I read: 2.4
Important concepts:
When there is more than one force that acts on an object, the subsequent motion of the object is then determined by the net force acting on the object. The net force is the vector sum of all the forces that are acting on the object. Newton’s first law says that an object acted on by zero net force moves in a straight line with constant speed or it remains at rest if it was at rest. Velocity vector is a measurement of both speed and the direction of an objects motion. There is no force required to keep an object in motion as long as there are no forces that oppose its motion. Inertia means resistance to changes in velocity. Newton’s first law can also be called the law of inertia. Reading Assignment Questions:

Explain the need for automobile seat belts in terms of Newton’s first law. Newton’s first law is an object in motion tends to stay in motion unless acted on by an opposing force. A car and seatbelts are connected together where the car goes the seatbelts go. The people in the car are not connected to the car. That is why they must be strapped in by the seatbelts. If the car had an accident of slammed on brakes really hard everyone would stay in motion that the car was in. Because the seatbelts are there to keep people in the same motion in the car it keeps a lot of people from being slung through the windshield. A freight train consists of an engine and several identical cars on level ground. Determine whether each of the statements is correct or incorrect and explain why. (a) If the train is moving at constant speed, the engine must be pulling with a force greater than the train’s weight. False the engine would have to be pulling with the same force as the trains’ weight. (b) if the train is moving at constant speed, the engine’s pull on the first car must exceed that car’s backward pull on the engine. True, if the engines pull did not exceed the backward pull of the first car the weight of the other cars would cause the train to not be able to maintain constant speed. (c) If the train is coasting, its inertia makes it slow down and eventually stop. False, the friction of the trains wheels and tracks would be what caused it to slow down. Reading Assignment #3: Newton’s Third Law...