The momentum of an object is the product of its mass and velocity. Mathematically, momentum is given as:
p = m x v
where, p is momentum, m is the mass of the object and v is its velocity.
In the given question, the mass of the object (m) is 5 kg and its velocity (v) is 10 m/s. Hence the momentum of the object is:
momentum, p = m x v = 5 kg x 10 m/s = 50 kg.m/s
Hence the momentum of the object is 50 kg.m/s.
Given the mass and velocity of any other object, we can calculate its momentum, using the same process. If this object were to collide with another object, in an isolated system, the total momentum would remain conserved, that is momentum lost by an object is equal to momentum gained by the other.
Hope this helps.