dynamics exam 3 concepts

T/F: linear momentum vector has the same direction as the acceleration

false, same direction as velocity

T/F: the principle of linear momentum can only be written for a single particle

false

T/F: every force acting on the particle's free body diagram will create an impulse

true

T/F: the initial momentum of the particle at time 1 plus the sum of all the impulses applied to the particle from t1 to t2 is equivalent to the final momentum of the particle at time t2

true

T/F: the principle of linear impulse and momentum can be solved in 2d, 3d and 1d modes

true

T/F: the velocity of the mass center for the system of particles does not change if no external impulses are applied to the system

true

what is the assumption for the conservation of momentum

the sum of the external impulses acting on a system of particles is zero

T/F: impulsive forces are very small compared to other larger forces

false, impulsive forces are very large and act for a short period of time

T/F: the conservation of linear momentum states that the total linear momentum for a system of particles remains constant during the time period t1 to t2

true

T/F: the internal impulses acting within the system are not considered in the impulse-momentum analysis

true, they cancel each other out (newtons third law) so are unnecessary to account for

T/F: in the analysis of impact, it is assumed that the particles have no initial momentum

false

T/F: at the moment of maximum deformation, the relative motion between the particles is zero

true, at this time they are moving w the same velocty

T/F: the coefficient of restitution is equal to the ratio of the relative velocity of the particles' separation just after the impact, to the relative velocity of the particles approach just before impact

true

T/F: if the collision between the two particles is perfectly elastic, the deformation impulse is equal and opposite to the restitution impulse

true, this is an ideal situation

T/F: after the plastic impact (collision) both particles couple or stick together and move w a common velocity

true

T/F: the sun of the moments about a point of interest of all the external forces acting on a system is equal to the time rate of change of the total angular momentum of the system about the same point of interest

true

T/F: if the particle moves along a space curve, the vector dot product can be used to determine the angular momentum about a point

false, the cross product

what is the condition for the conservation of angular momentum?

the angular impulses acting on a particle are all zero during the time of interest

what is a common unit for angular momentum?

kg•m^2/s

T/F: evaluating the determinant is a part of the scalar approach to angular motion analysis

false, vector approach

T/F: there are two types of rigid-body planar motion

false, translation, rotation about fixed axis, general plane motion

planar motion of a body occurs when all the particles of a rigid body move along paths which are...

equidistant from a fixed plane

what type of motion occurs when a line in the body remains parallel to its original orientation throughout the motion?

translation

the tangential acceleration measures...

the time rate of change in the magnitude of the velocity

T/F: points located on a body that rotates about a fixed axis follow a circular path

true

T/F: the general plane motion of a rigid body can be described as a combination of translation and rotation

true

which one is the correct set for describing the motion of a rigid body w translating and rotating components?

fixed reference, translating references

what does NOT contribute to the displacement of a point B on a rigid body which is not the base point for the analysis?

displacement due to rotation of the base point

what is the difference between the vector analysis approach and the scalar approach for relative velocity in rigid bodies?

vector analysis approach uses the cross product of angular velocity and the position vector to calculate the relative velocity term

T/F: in rolling w/o slipping, the center of the rolling rigid body rotated w constant velocity

false

T/F: the path described by points which define the location of the IC during the body's motion is called the centrode

true

T/F: the IC may be conveniently used to determine the velocity of any point in a body

true

T/F: the velocity of a point on the body is always perpendicular to the relative-position vector directed from the IC to the point

true

how many special scenarios are there for finding the location of the IC?

3

in rigid body analysis, the body is imagined as.... and .... at the IC

extended, pinned