Make sure you are familiar with units for
Mass: kilogram (kg)
Distance: metre (m)
Speed: metre per second (m/s)
Acceleration: metre per second squared (m/s^2)
Force: newton (N)
Time: second (s)
Gravity: newton/kilogram (N/kg)
the units of:
moment: Newton metre (Nm)
momentum: kilogram metre/second (kgm/s)
Forces can act on a body to change the velocity, so the speed, direction or both.
Or forces can change the shape of a body, stretching it squishing it or twisting it.
scalars are quantities with only magnitude (size)
vectors are quantities with magnitude (size) and direction
Force has a magnitude measured in (N) but it also has a direction, a push or a pull, up, down, left or right. So force is a vector.
momentum (kgm/s)= mass (kg) x velocity (m/s)
To reduce the force experienced by the passenger you need to extend the time for a passenger to stop in a collision. As force is the change in momentum divided by time.
Force is the rate of change of momentum. So Force (N) = change in momentum (kgm/s) / time (s)
Every action has an equal and opposite reaction.
Book pushes down on table, table pushes up on book. So book doesn’t accelerate.
Table pushes down on floor, floor pushes up on table. So table doesn’t accelerate.
moment = force x perpendicular distance from the pivot
The principle of moments states that when the clockwise moments are equal to the anticlockwise moments a body will be in equilibrium.
when moments are taken from the right hand side as the block is a greater distance the force from the left hand pivot must be bigger to counteract it. The opposite is true for the left hand side.
