Engineering Mechanics 1

Physical quantity is defined

• Quantity that can be measured

• Quantity to be find

• Quantity in laboratory

• Quantity that has direction

Define the following terms:

a)    Mechanics

b)    Coordinate System

c)    Force

d)    Moment

e)    Prefixes

Answer explanation

a)    Mechanics

Mechanics is the branch of physics concerned with the behaviour of physical bodies when subjected to forces and displacements, and the subsequent effect of the bodies on their environment.

b)    Coordinate System

A coordinate system is a method for identifying the location of a point on the earth. Most coordinate systems use two numbers, a coordinate, to identify the location of a point. Each of these numbers indicates the distance between the point and some fixed reference point, called the origin.

c)    Force

Force: the vector action of one body on another.
Force can be direct, i.e., contact or indirect, i.e., gravitational attraction.

A force has Magnitude, Direction and Point of application.

The SI unit of force in Newton (N) where by definition

d)    Moment

The Moment of a force is a measure of its tendency to cause a body to rotate about a specific point or axis.

This can be written as M=Fd, where M is the moment, F is the force, and d is the perpendicular distance. The units for measuring moments are Nm (newton-metres).

e)    Prefixes

Prefixes are used to represent very large or small values of physical quantities. They make it easier to work with values that are either too large or too small to be expressed in the standard unit of measurement.

Describe the following laws:

a)    Newton’s 1^st law

b)    Newton’s 2^nd law

c)    Newton’s 3^rd law

d)    Newton’s gravitational law

Convert 2 km/h to following units

(i)    m/s

(ii)    ft/s

• (i) 0.56

  (ii) 1.83

• (i) 0.65

  (ii) 1.38

• (i) 6.50

  (ii) 1.38

• (i) 1.56

  (ii) 0.83

1)    Evaluate each of the following and express with SI units having an appropriate prefix

(i)    (50 mN)(6GN)

(ii)    (400mm)(0.6MN)²

(iii)    45MN³/900Gg

• 300 mN²

  144 Gm.N²

  50 TN³/k

• 300 mN²

  14.4 Gm.N²

  50 TN³/k

• 300 kN²

  144 Gm.N²

  50 kN³/kg

• 300 kN²

  14.4 Gm.N²

  50 kN³/kg

Answer the following questions.

 

(i) A ball drops 5 meters. How many centimeters did it drop?

(ii)    Convert 10 m/s² to km/hr².

(iii)    The density of iron is 7.86 g/cm³ under standard conditions. Convert this to kg/m³.

• (i) 50 cm

  (ii) 1.296 x 10³ km/hr²

  (iii) 7.86 x 10⁵ kg/m³

• (i) 500 cm

  (ii) 1.296 km/hr²

  (iii) 7.86 kg/m³

• (i) 500 cm

  (ii) 7.296 x 10⁵ km/hr²

  (iii) 7.86 x 10³ kg/m³

• (i) 500 cm

  (ii) 1.296 x 10⁵ km/hr²

  (iii) 7.86 x 10³ kg/m³

Refer to the provided Figure, find the X and Y components for a force of 316N at 35 degrees.

•  Fx=181.25N

   Fy=258.85N

• Fx=258.85N

   Fy=181.25N

• Fx=258.85N

   Fy=258.85N

• Fx=181.25N

   Fy=181.25N

 Given that R is the result force of F1 and F2. Refer to the Figure Q8, find the R by using triangular geometry method.

• 1133.35 N

• 2673.12 N

• 2591.4 N

• 924.37 N