Given:
Mass of 90000 kg is lifted with an upward velocity of 0.12 m/s.
The mass is initially at rest and reaches its upward speed because of a net force of 6000 N exerted upward.
Want:
The time for which the force is applied.
Solve:
We can use the following kinematic equation to relate the force, mass, velocity, and time:
v = u + at
where
v is the final velocity (0.12 m/s)
u is the initial velocity (0 m/s, as the mass is initially at rest)
a is the acceleration, which can be calculated using Newton's second law of motion as F/m, where F is the net force (6000 N) and m is the mass (90000 kg)
t is the time for which the force is applied.
Substituting the given values, we get:
0.12 m/s = 0 m/s + (6000 N / 90000 kg) * t
Simplifying the right-hand side, we get:
0.12 m/s = (2/3) m/s^2 * t
Solving for t, we get:
t = (0.12 m/s) / ((2/3) m/s^2) = 0.18 s
Therefore, the force is applied for 0.18 s to lift the mass of 90000 kg with an upward velocity of 0.12 m/s.