Answer:
For an object to be an equilibrium it must be experiencing no acceleration.
Explanation:
Hope it helps.
Answer:
20 J
Explanation:
Given:
Weight of the book is, 
Height or displacement of the book is, 
The work done on the book to raise it to a height of 2 m on a shelf is against gravity. The gravitational force acting on the book is equal to its weight. Now, in order to raise it, an equal amount of force must be applied in the opposite direction.
So, the force applied by me should be equal to weight of the body and in the upward direction. The displacement is also in the upward direction.
Now, work done by the applied force is equal to the product of force applied and displacement of book in the direction of the applied force.
Therefore, work done is given as:

Therefore, the work done to raise a book to a height 2 m from the floor is 20 J.
Sound is an example of a mechanical wave. Mechanical waves are the kinds of waves that cannot be propagated without a medium. As such, these waves cannot travel through a vacuum, just like how sound cannot travel through space, since space is a vacuum.
Answer:
T = 1010 degree Celsius
Explanation:
mass of ball (Mb) = 100 g
mass of water (Mw) = 400 g
temp of water = 0 degree
specific heat of platinum (C) = 0.04 cal/g degree celsius
we can calculate the temperature of the furnace from the equation before
Mb x C x (temp of furnace (T) - equilibrium temp) = Mw x (equilibrium temp - temp of furnace)
100 x 0.04 x ( T - 10) = 400 x (10 - 0)
4 (T - 10) = 4000
T - 10 = 1000
T = 1010 degree Celsius
A girl standing on a floor would have two opposite forces acting on it. These forces are the weight and the normal force. Since no other forces are acting and that the girl is at rest, then the weight must equate to the normal force. Therefore, the supporting force would be:
F = mg = 55kg (9.81 m/s^2) = 539.55 N