If the net external torque acting on the particle is zero, the it satisfies - 1st condition of equilibrium - 2nd condition of equilibrium - Both 1st & 2nd condition of equilibrium - 2nd law of motion

a) the distances are zero, Both 1st & 2nd condition

c)  the torques are equal but of the opposite sign, 2nd condition of equilibrium

Explanation:

The equilibrium conditions are

1 translational

        ∑ F = 0

2 rotational

        ∑ τ = Σ (F_i x r_i) = 0

They tell us that external torque is zero.

Therefore we have two various possibilities

a) the distances are zero, in this case we have a pure translation movement

    for this situation the two equilibrium relations are fulfilled

b) the forces are zero, there is no movement

    It does not make sense to use the equilibrium relations since there are no forces

c) the torques are equal but of the opposite sign, the forces are on the opposite side of the body.

    In this case the 2 equilibrium relation is fulfilled, but not the first one that the force has the same direction

the minimum constant speed at which she can catch the train is 2.7 m/s

given:

acceleration = 0.6

time = 4.5 s

to find:

velocity = ?

formula used:

from 1st kinematic equation we get,

v = u + at

u = initial speed of train = 0 m/s

v = final speed of the train

a = acceleration of the train

t = time

solution:

from 1st kinematic equation we get,

v = u + at

u = initial speed of train = 0 m/s

v = final speed of the train

a = acceleration of the train

t = time

v = 0 + (0.6 × 4.5)

v = 2.7 m/s

the minimum constant speed at which she can catch the train is 2.7 m/s

the answer is ampere

the ampere is used to measure electricity. an ampere is a unit of electric current equal. a unit of measure for the flow of current in a circuit. one ampere is the amount of current flow provided when one volt of electrical pressure is applied against one ohm of resistance.