To do this, all you need to do is get the momentum of each and get the sum. The formula of momentum is:
p=mv
where: p = momentum m = mass v = velocity
Bicycle 1 and 2 have the same mass of 15 kg
Bicycle 1 v = 1 m/s Bicycle 2 v = 3 m/s but because it was coming from the opposite direction then we get a negative velocity. The negative just indicates the direction so it will be -3m/s
Their combined momentum before the crash is 30kg.m/s. We take out the negative sign because the question is asking only for the magnitude and not the direction and remember the negative sign indicates the direction.
Gravity varies when the Earth rotates and its mass and density differ based on where you are on the planet. Knowing how gravity affects sea level thus aids geodesists in making more precise calculations. The mean sea level would be higher in parts of the earth where gravitational forces are heavier.
