### 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

**radians**

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**

w must be in radians

**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**