Question

John is pushing a wheelbarrow filled with sand on a building site the total mass of the wheelbarrow and its content is 30kg. When he applies force of 20 the wheel barrow moves forward at constant speed. What is the Magnitude of the friction between the wheels and the ground?

Answer 1

Let the magnitude of friction force = f
acceleration ,a = 0 (because it moves with constant speed)
F=ma
20-f=30x0
f=20N

Answer 2

And curiously, that is the same magnitude of the friction between his shoes and the ground. Think on that, Newton.

Answer 3

Yes the magnitude will be the same until the force exceed the maximum frictional force then the system will only move with an acceleration.

Answer 4

so what about the gravity because they say between the wheels and the ground and we all know that the ground is the gravity which is 9.8 so dont we include force of gravity when finding the magnitude ?