An initially stationary box of sand is to be pulled across a floor by means of a cable in which the tension should not exceed 1130 N. The coefficient of static friction between the box and the floor is 0.390. (a) What should be the angle between the cable and the horizontal in order to pull the greatest possible amount of sand, and (b) what is the weight of the sand and box in that situation?

(a). if   = 0° , we can pull the greatest possible amount  of sand.

(b). The value of weight of sand and box = 2897.43 N

Explanation:

Maximum tension in the cable = 1130 N

The coefficient of static friction = 0.39

(a). Let the angle between the cable and the horizontal =

From the free body diagram, T = F ------ (1)

For maximum amount of force value of must be maximum, it is only possible when = 0°

⇒ = ° = 1

⇒ From equation (1)  we get

⇒T = F = 1130 N -------- ( 2 )

therefore if   = 0° , we can pull the greatest possible amount  of sand.

(b). From the free body diagram,

Force acting on the box F =

Put the value of F from equation 2 we get,

⇒ 1130 = 0.39  

⇒ = 2897.43 N --------- ( 3 )

From Free body diagram, Value of is equal to weight of the and and box.

⇒ = W

⇒ W = 2897.43 N

This is the value of weight of sand and box.

answer;

d. are made mostly of liquid

explanation;

-the general   composition and structure planets includes; they have a thick gas and liquid layer covering a small,solid core. mostly the gases are hydrogen and helium atmosphere and layers of liquid hydrogen. for instance neptune and uranus are examples of the outer planets, they have a core covered by ice and ammonia.

-neptune's atmosphere is hydrogen and helium with a bit of methane so there is no oxygen to breath and the interior is made up of frozen water and ammonia with a rock and iron core. thus, there is no liquid water or solid surface to survive.

what experimental evidence led scientists to change from the previous model to this one?

a few of the positive particles aimed at a gold foil seemed to bounce back.

the colors of light emitted from heated atoms had very specific energies.

experiments with water vapor showed that elements combine in specific proportions.

cathode rays were bent in the same way whenever a magnet was brought near them.