forces

Question 1

state the conditions for the equilibrium of a body which is acted upon by a number of forces

Answer 1

1. the net external force acting on the body is zero
2. the net torque on the body about any point is zero

Question 2

what is the property of an object in rotational equilibrium?

Answer 2

the line of action of the (three) forces must coincide at the same point

Question 3

what is the vector diagram that is seen when. an object is in translational equilibrium?

Answer 3

the vector addition of forces will form a close polygon

Question 4

what is a couple?

Answer 4

a pair of forces acting on the same body, which are equal in magnitude but opposite in direction, whose lines of action do not coincide // torque due to couple = xF regardless of pivot

Question 5

what is hooke’s law?

Answer 5

it states that the magnitude of force F exerted by a spring on a body attached to the spring is proportional to the extension x of the spring from its natural length provided the proportional limit to the spring is not exceeded //
F = kx

Question 6

what is upthrust?

Answer 6

the net upward force exerted by a fluid on a body fully or partially submerged in the fluid // net vertical force = weight of fluid displaced

Question 7

what is archimedes’ principle?

Answer 7

for a body submerged or floating in the fluid, upthrust acting on the body is equal in magnitude and opposite in direction to the weight of fluid displaced by the body
U = Vpg

Question 8

N1L

Answer 8

a body will continue in its state of rest or move at constant speed in a straight line unless an external resultant force acts on it

Question 9

N2L

Answer 9

the rate of change of linear momentum is directly proportional to the resultant force acting on it and its direction is in the same direction as this resultant force

Question 10

N3L

Answer 10

if body A exerts a force on body B, body B will exert an equal an opposite force on body A

Question 11

apparent weightlessness

Answer 11

no contact force acting on the body

Question 12

linear momentum of a body

Answer 12

the product of its mass and velocity

Question 13

impulse

Answer 13

the product of the average force acting on an object and the time interval that the force is being applied

Question 14

inelastic collision

Answer 14

1. KE decrease
2. total momentum before and after collision unchanged
3. perfectly inelastic - max KE lost

Question 15

elastic collision

Answer 15

1. KE unchanged
2. total momentum unchanged