Topic 3.2: Forces in action

Question 1

describe what happens when a resultant force F acts on a body with mass m

Answer 1

the body will accelerate in the direction of the resultant force . The resultant force is related to mass and acceleration by the formula:
f = ma

Question 2

what is meant by drag ?

Answer 2

an object moving through a fluid experiences a drag force acting on it. Drag is a frictional force that opposes motion
in air this is air resistance

Question 3

terminal velocity

Answer 3

when the forces acting on the falling object become balanced so the resultant force is 0
the acceleration becomes zero and the object is moving at maximum velocity

Question 4

what is the principle of moments ?

Answer 4

for an object in equilibrium , the sum of the clockwise moments is equal to the sum of the anticlockwise moments

Question 5

what is a moment ?

Answer 5

a turning force : force x perpendicular distance

Question 6

what is meant by a couple

Answer 6

a pair of equal and opposite coplanar forces that have a magnitude and opposite direction , applied to a body parallel to each other but not along the same line

Question 7

what is meant by density ?

Answer 7

the mass per unit volume of a substance .The unit is Kgm-3

Question 8

what is pressure ?

Answer 8

the normal force exerted on a surface per unit area . It is measured in Pascals (Pa)

Question 9

what is the force that an object submerged in a fluid experiences ?

Answer 9

it experiences an upwards force called thrust. This is because the pressure at the bottom surface of the object is greater than at its top surface

Question 10

Archimedes principle

Answer 10

The upthrust exerted on a body immersed in fluid , whether partially or fully submerged , is equal to the weight of the fluid that body displaces.
An object will sink if the upthrust is smaller than the weight
for a floating object , its weight is equal to the upthrust