Refer to the diagram shown below.
At A, the boy begins walking up the stairs.
At B, the boy is at the top of the slide. He has acquired PE (potential energy).
The value of the PE is
(50 kg)*(9.8 m/s²)*(11.5 m) = 5635 J
At C, the boy has KE (kinetic energy).
The value of the KE is
(1/2)*(50 kg)*(12 m/s)² = 3600 J
Energy is lost between B and C due to friction.
The lost energy is
5635 - 3600 = 2035 J
The distance traveled along the slide is 108 m.
If F = the average frictional force, then
(F N)*(108 m) = 2035 J
F = 18.84 N
Answers:
(a) The mechanical energy lost by sliding is 2035 J.
(b) The average frictional force is 18.84 N
Explanation:
Primary cell
1. They are non-rechargeable.
2. The energy density of primary cells is more.
3. The internal resistance of primary cells is more.
4. Example : Zinc-Carbon cell.
Secondary cells
1. They are rechargeable cells.
2. The energy density of secondary cells is less.
3. The internal resistance of secondary cells is less.
4. Example : Car batteries
Current :
The flow of electric charge per unit time is called electric current. It can be given by the formula as follows :

The SI unit of electric current is Ampere.
1 Ampere is defined as the current that flows with the electric charge of one Coulomb per second (C/s).
A manipulated variable is the independent variable in an experiment. It’s called “manipulated” because it’s the one you can change. In other words, you can decide ahead of time to increase it or decrease it. In an experiment you should only have one manipulated variable at a time. The manipulated variable is the independent variable in an experiment.