Statics-Test 1
If F={10i+10j+10k} N and G={20i+20j+20k} N, then F+G={_____} N
30i+30j+30k
Defines sines
A/sin(a)=B/sin(b)=C/sin(c)
Define the concurrent force system
Express each force as a Cartesian vector and add the i, j ,k componets of all the forces in the system. Fr=(sum)F=(sum)Fxi+(sum)Fyj+(sum)Fzk
A force of magnitude F, directed along a unit vector, U, is given by F=_____
F(U)
A force vector, ~F~, directed along a line defined by PQ is given by ______
F(~r_pq~/r_pq)
True or False A rigid body has a mass but negligible shape/size.
False
True or False If a vector, A, has the same magnitude as vector, B, then êa=êb.
False
What is the magnitude of the given unit vector, U? What are the angles relative to the coordinate axes? u=-0.456i-0.684j+0.569k
Magnitude=0 Coordinate axes= cos(alpha)i+cos(beta)j+cos(gamma)k cos(-0.456)i+cos(-0.684)j+cos(0.569)k
For a frictionless pulley and cable, tensions in the cable (T1 and T2) are related as _____.
T1=T2
What is not true about an unit vector?
it always points in the direction of positive x-axis
Vector algebra, as we are going to use it, is based on a _____ coordinate system.
right-handed
The dot product of two vectors results in a _____ quantity
scalar
Assuming you know the geometry of the ropes, in which system can you NOT determine forces in the cables? Why?
**choose drawing with 4 ropes** There are more unknowns than equations
Define position vector
A position vector locates one point in space relative to another.
Define scalar
A scalar is any positive or negative physical quantity that can be completely specified by its magnitude. Examples are length, mass, and time.
Define vector
A vector is any physical quantity that requires both a magnitude and direction for its complete description. Examples are force, position, and moment. A= (Axi+Ayj+Azk) m
True or False The subject called statics studies only body which are at rest.
False
The dot product of two vectors P and Q is defined as _____
PQcos(theta)
Find the magnitudes of the following unit vectors: U1=-0.8329i-942j+34k U2= 23.3/34i-3452/35654j+567/567k
U1=1 U2=1 unit vector is a vector whose magnitude is always 1
If F and r are force and position vectors, respectively, in SI units, what are the units of the expression (r*(~F~/F))?
meters
If a dot product of two non-zero vectors equals -1, then the vectors must be _____ to each other
parallel (pointing in the opposite direction)
If a dot product of two non-zero vectors is 0, then the two vectors must be ______ to each other?
perpendicular
P and Q are two points in 3-D space. How are the position vectors r_pq and r_qp related?
r_pq=-r_qp
Define the line of action of a force vector
straight line colinear with the force vector, F _ _ _ ______ _ _ _
The dot product can be used to find all of the following except _____
the sum of two vectors
When a particle is in equilibrium, the sum of forces acting on it equals _____.
zero
Find the dot product of the two vectors P and Q: P={5i+2j+3k} m Q={-2i+5j+4k} m
{-10+10+12} m^2 = 12 m^2
Two points in 3-D space have coordinates of P(1,2,3) and Q(4,5,6) meters. The position vector ~r_qp~ is given by _____
{-3i-3j-3k}m use P-Q
The position vector r_pq is obtained by
coordinates of Q minus coordinates of P
Define force equilibrium in 2D/3D
A body is said to be in force equilibrium when the resultant of all the forces acting on a body is zero. Fx=0, Fy=0, Fz=0
Define a free body diagram
A detailed drawing of an object in which the object is isolated (i.e. no supports) from its surroundings and all external forces acting on the body are shown
Define cosines
C=sqrt(A^2+B^2-2ABcos(c))
True or False If vector, A, is perpendicular to vector, B, then AxB=0.
False
Define the triangle rule for adding vectors
The resultant vector A+B is determined by the closing side of triangle by placing the vectors A and B "tip-to-tail"
Define parallelogram rule for adding vectors
The resultant vector is unaffected by the order of additive terms. R=A+B=B+A
True or False A particle has a mass but negligible shape/size.
True
For a force vector, the following parameters are randomly generated. The magnitude is 0.9 N, alpha=30, beta=70, gamma=100. What is wrong with this 3-D vector?
all three angles are arbitrarily picked, unit vectors are uniquely picked.
If you know only Ua, you can determine the _____ of A uniquely.
angles (alpha, beta, gamma)
The symbols, (alpha), (beta), and (gamma) designate the _____ of a 3-D Cartesian vector.
coordinate direction angles