Forces, Pressure and Dencity

Question 1

what is the center of gravity? (C.o.G)

Answer 1

it is the point at which the weight of an object may be considered to act

Question 2

what is meant by stability?

Answer 2

weather a object will or will not topple (fall over)

Question 3

what is the difference between C.o.G and C.o.M?

Answer 3

Center of gravity depends on the gravitational field
Center of mass does NOT depend on the gravitational field

Question 4

what is a moment?

Answer 4

the turning effect of a force?

Question 5

define moment or turning effect

Answer 5

moment = Force X perpendicular distance from the line of action to the pivot

Question 6

define equilibrium of an object

Answer 6

when an object is stationary or moving at a constant velocity.

aka: Resultant Force on the object = 0

Question 7

define rotational equilibrium

Answer 7

the net moment = 0
or
clockwise moment = anti-clockwise moment

Question 8

what is the definition of force

Answer 8

the rate of change of momentum

Question 9

true or false acceleration of free fall is not dependent on mass

Answer 9

True

Question 10

define Pressure

Answer 10

Force per unit area
p = F/A

Question 11

what is atmospheric pressure?

Answer 11

101 325pa or 101.325kpa

Question 12

define density

Answer 12

mass per unit volume
roh = m/V

Question 13

what is hydrostatic pressure?

Answer 13

the pressure that is exerted by a fluid at a given point within the fluid due to the force of gravity

Question 14

what is the formula to calculate hydrostatic pressure?

Answer 14

p = (roh) (g) (delta h)
where:
p = pressure
roh = density
g = the acceleration of gravity
h = hight of object

Question 15

what is archimedes principle?

Answer 15

an object submerged in a fluid has an upward buoyancy equal to the weight of the fluid displaced by the object

Question 16

True or false an object will float when the upthrust = weight of object

Answer 16

True

Question 17

define a couple

Answer 17

a pair of forces (of equal magnitude) acting in opposite directions that only produce rotation

Question 18

true or false a couple depends on a pivot

Answer 18

false

Question 19

what do you call the moment of a couple

Answer 19

Torque

Question 20

how do you calculate Torque (moment of a cople)

Answer 20

Force X Distance between forces

Question 21

can the forces in a couple share the same line of action?

Answer 21

no

Question 22

define upthrust (buoyancy force)

Answer 22

a force that pushed upwards on an object submerged in a fluid

Question 23

what causes upthrust?

Answer 23

a difference in hydrostatic pressure at the top and bottom of an object

Question 24

state the law of moments

Answer 24

for an object to be in equilibrium the clockwise moment must equal the anticlockwise moment

Question 25

what is the formula for a moment?

Answer 25

Force X perpendicular distance