PHYS 1305 REVIEW GUIDELINES FOR EXAM 1
Chapter 1:
1.
SI unit: Length in meters, Mass in kilograms, Time in seconds
2.
Conversion of Units
3.
Scientific Notation: Working with powers of 10
Chapter 2: Describing Motion
1.
Average Speed: s = d/t (where s is the average speed, d is the total distance, t is the total time) It can be expressed in m/s, miles/hr, ft/s, cm/s, etc.
From the above equation, d= s X t, and t= d/s. Instantaneous Speed = the average speed over a time interval that is very, very small.
2.
Speed with Direction: Velocity
V = ∆𝒙/∆𝒕 (where v is the average velocity, ∆x is change in displacement or total displacement, ∆t is the time interval or total time.) Note that velocity is vector. A
vector is a physical quantity that has both magnitude and direction. Examples of vectors are displacement, Examples are: distance, speed, length, population of
Houston, mass, how many, how much, how long, etc.
∆x = v X ∆t; and ∆t = ∆x/
3.
Average Acceleration is a =∆v/∆t, a= v f
– v i
/ t f- t i
. That is the change in velocity divided by the change in time.
(where a is the average acceleration, ∆v is the change in velocity, and ∆t is the time interval or total time or change in time.) Instantaneous acceleration is the change in velocity is change in velocity over a very, very small time.. Acceleration is expressed in m/s 2 .
4.
Free Fall: What goes up must come down is due to the force of gravity acting on the body near the surface of the earth drawing the body toward the center of the earth.
The force of gravity therefore is the force that planet earth exerts on any object on its surface pulling the object downward toward the center of the earth. It always points in the downward direction. Force of gravity has an acceleration g = -9.8 m/s associated with it. Just as the force of gravity, the acceleration due to the force of gravity always points downward. The force of gravity as well as its acceleration, decreases with increase in altitude. Weight is the effect of the force of gravity acting on an object pulling it downward. Therefore w= mg, where w is the weight expressed in newtons,
m is the mass expressed in kilograms, and g is the acceleration due to the force of
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gravity expressed which has a value of -9.8 m/s 2 near the surface of the earth.
Accordingly, weightlessness implies the situation where g, the acceleration due to the force of is approximately equal to zero, which is the case in outer space. The weight varies while the mass remains constant when an object is carried to outer space.
Chapter 3: Explaining Motion
1.
Objects move because enough forces act on them. There are two types of forces: contact forces and action-at-a-distance force or field force.
2.
Remember Newton’s three Laws of Motion as stated in class. Know each of them very thoroughly. Second Law equation is F = ma . Unit for force is Newton. IN = kg. m/s 2 .
3.
a = F/m, m = F/a.
4.
Free-body/Force Diagram drawn isolating the body from its surroundings and showing all the force, action and reaction forces, acting on the body and assuming the directions of these forces.
5.
Force of friction acts in the opposite direction to the force that causes motion. It is a resistive force existing between two interacting surfaces. There are two types of frictional forces: force of static friction, f s
≤µ s
n is the force that holds an object in place or at rest. Motion takes place when applied force equals force of static friction.
Force of kinetic friction f s
= µ k
n, this is the force that occurs when motion takes place.
It is a force that has one to contend with while motion is in progress. (
µs and µk
are called the coefficient of static friction and kinetic friction respectively and depend on the nature of the two surfaces in contact and not on the area of the surfaces.)
Chapter 4: MOTION IN SPACE
1.
When an object moves in circle, the displacement change ϴ is circular in nature and is expressed in radians.
2.
Different parameters are used to express the velocity and the acceleration: ώ and
α, respectively.
3.
Centripetal acceleration , a c
is due to the change in the velocity direction only and it points toward the center of the circular path. That is why it is called center seeking/pointing acceleration. Centripetal acceleration is produced by centripetal force which also points toward the center. Centripetal acceleration, a c =
v
2
/r, Fc = ma
2
= mv
2
/r. Centripetal force plays numerous roles in circular motion.
4.
Projectile motion is a two dimensional motion where the displacement, velocity and acceleration has components in both the horizontal, X, and the vertical, Y directions.
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5.
Motion is constant in the horizontal direction, that is velocity is constant in the horizontal direction and there is no acceleration in the horizontal direction.
6.
On the other hand, motion is not constant in the vertical direction, the vertical component of the velocity varies because there is an acceleration in the vertical direction, that is, g, the acceleration due to the force of gravity.
7.
The maximum distance traveled by a projectile is called the Range, R= 2(Vocosϴ
0
)t.
8.
In general, a projectile motion is a mirror image of a free fall.
9.
The motion of the rim of a bicycle tire and that car tire is called rotational motion.
10.
Rotational motion is produced by a twisting force called torque. Therefore, torque is a twisting force that causes rotation. Torque is responsible for most of the external motion of the human body.
Chapter 5: Gravity
1.
The concept of the force of gravity and its associated acceleration was clearly explained by Isaac Newton. According to him, an object near the surface of the earth falls down with an acceleration of 9.8 m/s every second. He also came up with the Law of Universal Gravitation, F = Gm
1
m
2
/r 2 , where m
1
and m
2
are the masses of the two objects. G, the constant = 6.67 X 10 -11 N.m
2 /kg 2 = 0 .0000000000667 N.m
2 /kg 2 .
2.
Near the surface of the earth, g = F/m= GM E /RE 2 . = 9.8 m/s 2 , once we know the mass of the earth. As mentioned above, g, varies with altitude. That means that a passenger in an airplane flying many kilometers above the surface of the earth should weigh less.
3.
Tides are caused by earth’s rotation and because of the bulginess of the surface of the earth surface.
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5.
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