QUIZ - MMJ10203 DYNAMICS ENGINEERING

A construction worker is worried about applying too much torque to a bolt using his wrench.  What could he do to reduce his torque on the bolt?

• 
  Increase the length of the wrench

• 
  Increase the force on wrench

• Reduce the length of the wrench

• 
  Reduce the friction between the bolt and wrench

The moment of inertia:

• is synonymous with mass

• does not depend on where the mass is located

• 
  resistance to a change in rotational inertia

• 
  more resistance to change = less inertia

In rotation of rigid body, if a system is in static equilibrium, it must have the following 2 conditions

• Στ = 0

• Constant acceleration

• ΣF = 0

• Positive forces only

The moment of a 50 N force 20 cm away from the pivot point will be...

• 500N

• 20 Nm

• 10 Nm

• 15Nm

Systems I and II are made up of the same rigid body having its center of mass at point G and moving in a HORIZONTAL PLANE. In System I, the body is pinned to ground at G,whereas in System II the body is pinned to ground at point A, which is an aribitrary non-centroidal point. A couple M acts of each body. Let and represent the angular accelerations of the bodies in Systems I and II, respectively.

Which of the following best represents the comparison of the two angular accelerations?

• | α_I | < | α_II |

• | α_I | = | α_II |

• | α_I | > | α_II |

In System I, a homogeneous disk of radius R and mass m is able to roll without slipping as it moves along a rough horizontal surface under the action of force F. In System II, the same disk now moves along a rough (µk = 0.3) horizontal surface but here the disk slips as it rolls under the action of the same force F. Let (α_O)I and (α_O)II represent the angular acceleration of the disks’ centers O, for Systems I and II, respectively.

Which of the following best represents the comparison of the accelerations (α_O)I and (α_O)II ?

• (α_O)I < (α_O)II

• (α_O)I = (α_O)II

• (α_O)I > (α_O)II

A thin, homogeneous bar has a mass m and a length of L. End A of this bar is constrained to move within a smooth, horizontal guide. A force F acts in the horizontal direction at end B. Let a_A represent the acceleration at end A of the bar.

Which of the following best represents the direction of the acceleration of end A?

• a_A is to the left

• a_A = 0

• a_A is to the right

A 75 kg man and 40 kg girl sit on the seasaw, which has negligible mass. Assuming the girl sit 2 meter from the center of the seasaw and the man sit 1.5 meter from the center of the seasaw. Draw free body diagram of the seasaw which show all the forces applied to it together with its value

Write the general equation for Work and Energy of Rigid Bodies