When someone lifts a book from the ground, the work you use is positive. By lifting the book, you change it's energy and it's original place The book gains, kinectic energy.
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Answer:
The frictional force
6.446 N
The acceleration of the block a = 6.04 
Explanation:
Mass of the block = 3.9 kg
°
= 0.22
(a). The frictional force is given by


3.9 × 9.81 × 
29.3 N
Therefore the frictional force
0.22 × 29.3
6.446 N
(b). Block acceleration is given by

F = 30 N
= 6.446 N
= 30 - 6.446
= 23.554 N
The net force acting on the block is given by

23.554 = 3.9 × a
a = 6.04 
This is the acceleration of the block.
Answer:
Explanation:
The law of inertia states that if an object is in motion will remain in motion unless an external force is applied to it.
law of inertia for the rotating system in terms of angular momentum states that the angular momentum of a system will remain the same unless an external torque is applied to the system.
External Torque either increases or decreases the angular velocity thus changing angular momentum.