1.) emily leaves her physics book of mass 1 kg on the top of the table that is inclined at an angle of 20°. what is the acceleration of the book if the coefficient of kinetic friction between the book and the inclined plane is 0.3
2.) a boy pulls a toy cart of mass 2 kg with a force of 3 n at an angle of 60° with respect to the horizontal road. what is the acceleration produced by the cart?
3.) a man pulls a suitcase of mass 15 kg with a force "f" inclined at an angle of 60° to the horizontal. the frictional force between the floor and the wheels of the suitcase is 10 n. what is the force required to produce an acceleration of 0.1 m/s2 on the suitcase?
4.) the net force on a sailboat is 252 n, while the wind exerts a force of 325 n. what is the water-resistant force acting on the sailboat?
5.) a parachutist of mass 75kg descends with an acceleration of 8 m/s2. what is the upward force exerted by the air on the parachutist?

In all the problemas we consider the gravity acceleration equals to 10 m/s2

1) Applying the 2nd law of Newton:

1x10xsin(20°) - 0.3x10xcos(20°) = 1xa

a = 0.6011 m/s2

2) Applying the 2nd law of Newton:

3 - 2x10xsin(60°) = 2xa

a = -7.1602 m/s2 (The negative sign means that the cart is going down)

3)  Applying the 2nd law of Newton:

F - 15x10xsin(60) - 10 = 0.1x15

F = 141.4038 N

4) Applying the 2nd law of Newton:

Net force = 325 - F = 252

F = 73 N

5) Applying the 2nd law of Newton:

75x10 - F = 75x8

F = 150 N

b) mutualism

hope this : )

explanation:

metals have excess of electrons whereas non-metals have deficiency of electrons. thus, in order to gain stability metals easily donate their electrons to the non-metals.

for example, electronic configuration of sodium is and electronic configuration of phosphorous is .

when a phosphorous atom and sodium atom combine together then sodium will donate is extra one electron to the phosphorous atom. as a result there will be formation of ionic bond between sodium and phosphorous.

the reaction will be as follows.

there, are three sodium sodium atoms and each of them will donate its one extra electron to phosphorous atom. thus, the sub-shell of phosphorous gets completely filled.  

thus, we can conclude that electrons are transferred from atoms of sodium to atoms of phosphorous. this transfer makes the sodium atoms donate one electron and the phosphorous atoms to gain one electron. as a result, the sodium and phosphorus atoms strongly attract each other.