Kinematics and Dynamics

Question 1

What units make up the base units of the SI system?

Answer 1

length= meter
mass=kilogram
time= second
current= ampere (=C/s)
amt of substance = mole
temperature = kelvin
luminous intensity= candela (cd)

Question 2

What are important derived units in the SI system?

Answer 2

force= newton = kgm/s^2
work and energy= joule= kgm^2/s^2
power= watt= kg*m^2/s^3

Question 3

if the newton is the product of kilograms an dmetters/second^2, what units comprise the pound?

Answer 3

none it is a base unit in the imperial system. it is used for weight.
slug*ft/s^2

Question 4

Which quantities are vectors and which are scalar?

Answer 4

vectors- displacement, velocity, acceleration, force

scalars- distance speed energy pressure and mass

Question 5

How to do vector addition?

Answer 5

Add vectors tail to tip or break them into their componet vectors using sohcahtoa and pythag. theorem.

Question 6

I needed a scalar quantity like work, how would i multiple the vectors?

Answer 6

by the dot product-
A(dot)B=abs(A)*abs(B) cos theta
the two vectors of interest would be force and displacement

Question 7

If I need a third vector like torque, how would i multiple the org. vectors?

Answer 7

by cross product-
A x B=abs(A)*abs(B) sin theta
the two vectors of interest would be force an lever arm

Question 8

displacement vs distance

Answer 8

displacement- vector quantity that connects the objects initial and final position
Distance- scalar quantity of the total distance traveled b the object

Question 9

what is the relationship between instantaneous speed and velocity?

Answer 9

they are equal when considering the magnitude of the instantaneous velocity ( measure of the avg velocity as the change in time approaches zero)

Question 10

velocity vs speed

Answer 10

velocity- vector whose magnitude is the rate of change of displacement in given time
speed- rate of distance traveled in a given time

Question 11

What forces can act on an object by touching?

not touching?

Answer 11

force on touch- mechanical manipulation, friction

force no touch- gravity, electrostatics, magnetic, nuclear

Question 12

If the r is doubled in the gravitational force eqn how will it affect F_g? tripling m_1?

Answer 12

2*r->F_g/4

3m_1->3F_g

Question 13

What do you need to consider when calculating the static friction vector?

Answer 13

the coefficent of static fiction, the normal force on the object, and that friction always opposes an object’s motion
-stationary objects might not be experiencing a maximal static force of friction

Question 14

when does kinetic friction come into play?

Answer 14

when an object begins sliding
a rolling object only means static
its also a constant value that depends on the coefficient of kinetic friction and the normal force but static can be from 0 to maximum

Question 15

Where is the center of mass of an object?

Answer 15

the geometric center, only if the object is homogeneous ( in shape and density)

Question 16

When no force is applied the velocity is…?

Answer 16

Constant, no force means no acceleration so the object must be at constant velocity

Question 17

what can velocity vs time graphs tell you about acceleration?

Answer 17

a positive slope will tell you there is acceleration

a negative slope will tell you there is decelleration

Question 18

What is the law of inertia?

Answer 18

first law-mass will be at rest or in motion at a constant velocity until a net force acts upon it

Question 19

what is a move generalized way to look at the law of inertia?

Answer 19

second law-a net force must act upon an object for it to accelerate

Question 20

Why do the moon and the earth have a balanced gravitational force on each other?

Answer 20

third law- for every application of force on an object, the object will apply an equal and opposite force back on the first

Question 21

When air resistance is not negligible what happens to an object in free-fall

Answer 21

it will reach terminal velocity because the drag force from the air will eventually reach the same magnitude as the weight of the object and it will fall at a constant velocity.

Question 22

What are four equations that relate acceleration, velocity and/or position? (regarding one dimensional motion)

Answer 22

v=v_0+at
x=v_0+(at^2/2)
v^2=v_0^2+2ax
x=v_constant*t

Question 23

what relationships will you use to help solve projectile motion and inclined plane problems?

Answer 23

SOHCAHTOA

you’ll need to know the angle of trajectory or the angle of the inclined plane

Question 24

why would an object discontinue motion in a circular path?

Answer 24

it exits when the centripetal force no longer acts upon it allowing the object to continue in a path tangential to the the circle at that point.

Question 25

centripetal force eqn

Answer 25

F_c=(mv^2)/r

Question 26

What basic concept can be useful when drawing free body diagrams?

Answer 26

breaking the forces into force components (trig) and then summing the ones in the same direction

Question 27

to solve problems relating to translational equilibrium what concepts must you remember?

Answer 27

free-body diagrams and newtons three laws

Question 28

What is torque

Answer 28

moment of force is generated by the application of force at some distance form the fulcrum
~t=r x F= r*Fsin theta
-~t= clockwise
+~t= counter clockwise

Question 29

How to lift a heavy object with a lever

Answer 29

place the object close to the fulcrum and made the your downward force distance from the fulcrum much longer than the fulcrum distance to the object