The bi in bicycle actually means two, so by definition a vehicle with another number of wheels is something else. There are unicycles, trikes, pedal cars and HPVs(Human Powered Vehicles) .
There are two wheels on a bike.
Friction between the wheelbarrow wheels and the ground allows the wheelbarrow to move when force is applied. Without friction, the wheels would simply slip and the wheelbarrow wouldn't move forward easily. However, too much friction can make it harder to push the wheelbarrow.
wheelbarrow
A wheelbarrow uses wheels.
Wheelbarrow is spelt exactly as you have spelt it. It is a "barrow" on "wheels": hence, "wheelbarrow".
It depends on the wheelbarrow
A wheelbarrow has 1 wheel for maneuverabilty. Although they do have bigger barrows that have two wheels. However, if they are too widely spaced, they need to be able to pivot.
It depends on the size of the wheelbarrow.
the wheels go round and round up and down side to side very flexible easy to use
ask your local DIY store for 4 wheelbarrow wheels and tires. In the US it would be about $60 a set and in UK is £45.
a wheelbarrow
Somewhere between, 0,08 and 0,12 depending on your wheelbarrow.
A wheelbarrow is an example of two simple machines, a class 2 lever and a wheel and axle.