# Force Moment Velocity Distance Physics

### Force Moment Velocity Distance Physics

This Physics chapter is about Force, Moment, Velocity and Distance.

the line of action is

an extended line drawn colinear with the force

the lever arm is the

distance ι between the line of action and axis of rotation, measured on a line that is perpendicular to both

magnitude of torque =

magnitude of force x lever arm

the torque is positive when…

the force tends to produce a counterclockwise rotation about the axis

if a rigid body is in equilibrium, neither…

its linear motion nor its rotational motion changes

a rigid body is in equilibrium if it has

zero translational acceleration and zero angular acceleration

in equilibrium, the sum of externally applied forces is

zero

torque is what causes _____ ______ to change

rotational motion

the choice of axis is completely arbitrary, because if an object is in equilibrium, it is in equilibrium with respect to…

any axis whatsoever

to a large extent, the directions of the forces acting on an object in equilibrium can be deduced using

intuition

choosing the direction of an unknown force backward in the free body diagram simply means that

the value determined will be a negative number

center of gravity of a rigid body is the point at which…

the weight can be considered to act when the torque due to the weight is being calculated

when an object has a symmetrical shape and its weight is distributed uniformly, the center of gravity lies

at its geometrical center

the center of gravity plays an important role in determining whether a group of objects remains in

equilibrium as the weight distribution within changes

according to newton’s second law for rotational motion about a fixed axis, the net external torque is directly proportional to

the angular acceleration

moment of inertia of the particle

I = mr²
-the constant of proportionality between the torque and acceleration

moment of inertia (I) of the body:

sum of the individual moments of inertia
∑mr²

moment of inertia of the body equation

I = m₁r₁² + m₂r₂² = ∑mr²

when forces act on a rigid object, they can affect its motion in two ways:

1) produce translational acceleration (ax and ay)
2) produce torques, causing the object to have angular acceleration α

for translational acceleration (ax ay) we use:

∑F=ma

for rotational motion of rigid object around fixed axis

∑t=lα

the work done W by a constant force that points in the same direction as displacement is

W=Fs

the rotational work done Wr done by a constant torque T in turning an object through an angle θ is

Wr = Tθ

for rotational work (Wr), θ must be expressed in

rotational kinetic energy: KEr of a rigid object rotating with angular speed w about a fixed axis and having a moment of inertia I is:

KEr = 1/2lw²

angular momentum L of a body rotating around a fixed axis is the product of the body’s moment of inertia I and its angular velocity with respect to that axis:

L = lw

principle of conservation of angular momentum

when the sum of average external torques is zero, final and initial angular momenta are the same

Lf = Lo

Is it possible for two quantities to have the same units but different dimensions?

no

Is it possible for two quantities to have the different units but the same dimensions?

yes

kilo

10^3

deci

10^-1

centi

10^-2

milli

10^-3

Micro

10^-6

nano

10^-9

pico

10^-12

mega

10^6

giga

10^9

tera

10^12

peta

10^15

On a fishing trip, you catch a 2.8 lb bass, a 13.9 lb rock cod, and a 15.33 lb salmon.

32.03 lb

How many significant figures are in 0.00000303?

3

How many significant figures are in 6.201*10^5?

4

Which of the following quantities have the dimensions
of time? (a) x/v (b) a/v (c) (2x/a)^1/2 (d) v^2/a

x/v, (2x/a)^1/2

The accuracy of an instrument is called what?

resolution

Typically resolution is ______ the smallest division on an instrument.

1/10

___________ is the total length of travel.

Distance

_______ is the change in position.

Displacement

Average speed =

Distance/elapsed time

Average velocity =

Displacement/elapsed time

What are the three vectors associated with one dimensional movement?

displacement, velocity, acceleration

A vector has what and what?

magnitude and direction

The instantaneous velocity at a point is equal to what?

The slope of the tangent line to the curve at that point

Acceleration is what?

change in velocity/time

When acceleration and velocity are in the same direction an objects speed will

increase

When acceleration and velocity are in opposite directions an objects speed will

decrease

When acceleration is perpendicular to velocity an object is

turning

When acceleration is constant velocity can be given by the equation

v = v0+at

When acceleration is constant the average velocity can be found by the equation

1/2(v0+vf)

When an object is in free fall it is only subject to the influence of

gravity

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