A particle of mass 40kg is resting on a rough horizontal table and can just be moved by a force of 10Kg wt (10g N) acting horizontal. Finda)The coefficient of frictionb)The greatest pushing...

A particle of mass 40kg is resting on a rough horizontal table and can just be moved by a force of 10Kg wt (10g N) acting horizontal. Find
a)The coefficient of friction
b)The greatest pushing force that can be applied at an angle go 50 degrees to the horizontal without moving the particle. 
A buoy of mass 4kg is held 5m below the surface of the water by a vertical cable. There is buoyancy force (upwards) of 42n acting on the buoy. Find the tension in the cable.
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2 Answers
1. When a body of mass m placed on a rough surface has to be moved, the force that needs to be applied is equal to F = m*g*C where g is the gravitational acceleration and C is the coefficient of static friction.
The particle of mass 40 kg can be moved by a force equal to 100 N. Substituting the values in the equation provided 100 = 40*10*C, here g is taken as 10 m/s^2.
C = 100/400 = 0.25
When a force F is applied at an angle 50 to the horizontal, the component parallel to the horizontal is F*cos 50. To determine the maximum value of F that can be applied without moving the particle solve F*cos 50 = 100
F = 100/cos 50
=> F `~~` 155.572. A buoy of mass 4 kg is held 5 m below the surface of the water by a vertical cable. The tension in the cable is the difference between the buoyancy force acting upwards and the gravitational force of attraction acting downwards. The latter is equal to 4*9.8 = 39.2 N. The tension in the cable is equal to 42  39.2 = 2.8 N
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hi, thankyou, but the answer to 1b is 117N and could you also do the engine question for the image attached as well.
thanks :)
this was the other question that I attached. the one for the image

An engine of mass 60 000kg is pulling a truck of mass 12 000kg at constant speed up a slope inclined at x to the horizontal, where sinx=1/200
Respective frictional resistances are 50N per 1000kg for the engine
Calculate
a)the tractive force exerted by the engine
b)The tension in the coupling between the engine and the truck
Ans: a) 6888n b) 948N
Show diagrams, and write an equation for each force in vector form (xi+yj)
how did u get 100 N???
hi, thankyou, but the answer to 1b is 117N and could you also do the engine question for me as well.
thanks :)