Answer:
If the system consists of the block only, the work done by the gravity is negative.
If the system consists of the block and the earth the work done by the gravity is zero.
Explanation:
If the system consists of the block only, then the system experiences two external forces: one exerted by the hand that lifts the block vertically upward and other exerted by the earth (gravity), which is opposed to the movement of the system, so the work done by gravity is negative.
On the other hand, if the system consists of the block and the earth, then only exists a external force which is the exerted by the hand. So, the force exerted by gravity is zero.
The gravitational force between a mass and the Earth is the object'sweight. Mass is considered a measure of an object's inertia, and its weight is the force exerted on the object in a gravitational field. On the surface of the Earth, the two forces are related by the acceleration due to gravity: Fg = mg.
Hoped this helped!
Answer:
25 N
Explanation:
Work is a product of force and perpendicular distance moved.
W=Fd where F is force exerted and d is perpendicular distance.
However, for this case, the distance is inclined hence resolving it to perpendicular so that it be along x-axis we have distance as 
Therefore, 
Making F the subject of the formula then
where
is the angle of inclination. Substituting 190 J for W then 18 degrees for
and 8 m for d then
Answer:



Explanation:
g = Acceleration due to gravity = 
= Angle of slope = 
v = Velocity of child at the bottom of the slide
= Coefficient of kinetic friction
= Coefficient of static friction
h = Height of slope = 1.8 m
The energy balance of the system is given by

The speed of the child at the bottom of the slide is 
Length of the slide is given by


The force energy balance of the system is given by

The coefficient of kinetic friction is
.
For static friction

So, the minimum possible value for the coefficient of static friction is
.
B verifying is the answer