Assume you get a summer job as a crane operator. on the first day you are lifting a heavy piece of machinery. even though you have the arm at 70∘ above the horizontal, the crane begins to tip slowly forward. consider the following possible actions: release the brake on the lifting cable so that the load accelerates downward. release the lifting arm so that θ decreases rapidly and the load accelerates downward. increase θ while simultaneously letting out the lifting cable so that the load accelerates downward. put the crane wheels in gear and accelerate the crane forward. none of these solutions is ideal, but which will have the short-term effect of restoring contact of the crane's rear wheels with the ground? a) all but 1 b) all but 2 c) all but 3 d) all but 4 e) all of them

d) physical means can be used to separate the components of air.

weight of the box is given as

here this is placed on the inclined of angle 42 degree

now this weight will have two components one is along the incline other is perpendicular to it

so here we need to apply a force parallel to incline opposite to its component of weight

so here the component of weight is given as

here we have

so it requires 75 n force to move it upwards

speed of light in vacuum is 300,000 km/s

speed of light in other mediums is given by the expression v = c/n, where c is the speed of light in vacuum and n is the refractive index of medium.

for the first medium v = 200,000 km/s

  so, refractive index of medium = 300000/200000 = 1.5

    1.5 refractive index is usually for glass. so first medium is glass.

for the second medium v = 250,00 km/s

so, refractive index of medium = 300000/250000 = 1.2

    1.2 refractive index is usually for water. so second medium is water.

for the third medium v = 0 km/s

so, refractive index of medium = 300000/0 = ∞

    ∞ refractive index is usually for opaque mediums. so third medium is opaque medium.