The frictional force is 218.6 N
Explanation:
The block in the problem is at rest along the inclined surface: this means that the net force acting along the direction parallel to the incline must be zero.
There are two forces acting along this direction:
- The component of the weight parallel to the incline, downward along the plane, of magnitude

where
m = 46 kg is the mass
is the acceleration of gravity
is the angle of the incline
- The (static) frictional force, acting upward, of magnitude 
Since the block is in equilibrium, we can write

And substituting, we find the force of friction:

Learn more about frictional force along an inclined plane:
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Let's use ' t ' to represent half of the time, in hours.
The distance traveled in the first half of the time is (80 t) km.
The distance traveled in the last half of the time is (40 t) km.
The total distance covered is (80t + 40t) = (120t) km.
You said that the total distance covered was 60 km,
so ...
120 t = 60 km
Divide each side by 120 : t (half of the time) = 0.5 hour
Average speed = (total distance covered) / (time to cover the distance)
= (60 km) / (1 hour)
= 60 km/hr .
Answer:
1. Hot air is less dense and has moved upward allowing cool air to move downward which is less dens
(Convection current)
2. The ceiling has transferred heat to him by radiation.
Explanation:
During the day when air is heated as a result of the ceiling transferring heat to it, it becomes less dens and it gains energy, which make it lighter in weight than cooler air, this hot air moves upward allowing cooler air to move downward.
Answer:

Explanation:
= Avogadro's number = 
e = Charge of electron = 
k = Coulomb constant = 
Z = Atomic number of water = 18
M = Molar mass of water = 0.018 kg/mol
m = Mass of person
The charge is given by

Total number of protons and electrons in each sphere




Electrical force is given by

The electrostatic force of attraction between them is 