25 Questions
Engineering Mechanics is a branch of the physical sciences that is concerned with the state of rest or motion of bodies subjected to the action of ______.
forces
Statics is concerned with the equilibrium of a body that is either at rest or moves with constant ______.
velocity
Dynamics is the study of external effects of forces in a moving ______.
body
Strength of Materials deals with the relationship between loads and their internal effects on a ______.
body
A force system is any arrangement where two or more forces are acting on a body or group of related ______.
bodies
Two forces are in equilibrium if they are equal and oppositely ______ directed.
opposite
Friction is a retarding force that always acts opposite to the motion or to the tendency to move. Types of Friction Dry friction, also called ______, occurs when unlubricated surfaces of two solids are in contact and slide or tend to slide from each other. If lubricant separates these two surfaces, the friction created is called ______ friction.
static, kinetic
Fluid friction occurs when layers of two viscous fluids moves at different velocities. The relative velocity between layers causes frictional forces between fluid elements, thus, no fluid friction occurs when there is no relative velocity. Skin friction also called friction drag is a component of the force resisting the motion of a solid body through a fluid. Internal friction is associated with shear deformation of the solid materials subjected to ______ loading.
cyclical
Elements of Dry Friction N� = Total reaction perpendicular to the contact surface f� = Friction force μ� = Coefficient of friction R� = Resultant of f and N ϕ� = angle of friction i. Centroids -- is the center of gravity of any plane which has no weight or mass only it has area, volumes and lines, etc. ii. Center of gravity – it is the part o f the body thru which the action line of weight, W, will always pass. iii. Axis of reference -- it is usually the lowest line of the geometric figure for calculated the Ȳ and the left the figure for calculating Ẋ iv. Axis of symmetry -- it is usually the x-x axis or the y-y–axis where the center of gravity or centroid of the body lies. PROBLEMS SOLVING FOR PART 1: Problem 51 The block A in Fig. P-544 supports a load W and is to be raised by forcing the wedge B under it. If the angle of friction is 10° at all surfaces in contact, determine the maximum wedge angle α that will give the wedge a mechanical advantage; i.e., make P less than the weight W of the block. Problem 52 A uniform bar AB, weighing 424 N, is fastened by a frictionless pin to a block weighing 200 N as shown in Fig. P-533. At the vertical wall, μ = 0.268 while under the block, μ = 0.20. Determine the force P needed to start motion to the right. Problem 53 What weight W is necessary to start the system of blocks shown in Fig. P-510 moving to the right. The coefficient of friction is 0.10 and the pulleys are assumed to be frictionless. Problem 54 As shown in Fig. P-529, a homogeneous cylinder 2 m in diameter and weighing 12 kN is acted upon by a vertical force P. Determine the magnitude of P necessary to start the cylinder turning. Assume that μ = 0.30. Problem 55 A wedge is used to split.
What is the study of external effects of forces in a moving body called?
Dynamics
What is the type of friction that occurs when unlubricated surfaces of two solids are in contact and slide or tend to slide from each other?
Dry friction
What does Strength of Materials deal with?
The relationship between loads and their internal effects on a body
What is the branch of the physical sciences concerned with the state of rest or motion of bodies subjected to the action of forces?
Engineering Mechanics
What is the condition for two forces to be in equilibrium?
Equal and oppositely directed
What is the maximum wedge angle that will give the wedge a mechanical advantage when forcing the wedge under the block?
Determine the maximum wedge angle α
What is the angle of friction in Problem 51?
10°
In Problem 52, what is the coefficient of friction at the vertical wall?
0.268
What is the coefficient of friction under the block in Problem 52?
0.20
What is the coefficient of friction in Problem 53?
0.10
In Problem 54, what is the coefficient of friction assumed to be?
0.30
What type of friction occurs when unlubricated surfaces of two solids are in contact and slide or tend to slide from each other?
Dry friction
What is Skin friction also known as?
Friction drag
What is the study of external effects of forces in a moving body called?
Dynamics
What does Strength of Materials deal with?
The relationship between loads and their internal effects on a body
What does Statics concern?
The equilibrium of a body that is either at rest or moves with constant velocity
Study Notes
Engineering Mechanics
- Engineering Mechanics is a branch of the physical sciences concerned with the state of rest or motion of bodies subjected to the action of forces.
Subfields of Engineering Mechanics
- Statics is concerned with the equilibrium of a body that is either at rest or moves with constant velocity.
- Dynamics is the study of external effects of forces in a moving body.
- Strength of Materials deals with the relationship between loads and their internal effects on a body.
Force Systems
- A force system is any arrangement where two or more forces are acting on a body or group of related bodies.
Equilibrium
- Two forces are in equilibrium if they are equal and oppositely directed.
Friction
- Friction is a retarding force that always acts opposite to the motion or to the tendency to move.
- Types of Friction:
- Dry friction (also called Coulomb friction) occurs when unlubricated surfaces of two solids are in contact and slide or tend to slide from each other.
- Fluid friction occurs when layers of two viscous fluids move at different velocities.
- Skin friction (also called friction drag) is a component of the force resisting the motion of a solid body through a fluid.
- Internal friction is associated with shear deformation of solid materials subjected to loading.
Elements of Dry Friction
- N = Total reaction perpendicular to the contact surface
- f = Friction force
- μ = Coefficient of friction
- R = Resultant of f and N
- ϕ = angle of friction
Centroids and Center of Gravity
- Centroids are the center of gravity of any plane which has no weight or mass, only area, volumes, and lines.
- Center of gravity is the part of the body through which the action line of weight, W, will always pass.
- Axis of reference is usually the lowest line of the geometric figure for calculating Y and the left of the figure for calculating X.
- Axis of symmetry is usually the x-x axis or the y-y axis where the center of gravity or centroid of the body lies.
Test your knowledge of fundamental areas of engineering mechanics including statics, dynamics, and strength of materials. Explore concepts related to the equilibrium of bodies, the effects of external forces, and the relationships within materials.
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