Having freckles is dominant (F) and not having freckles is recessive (f), A mother has Ff and a father has Ff , if they have a child which genotype will make the child have freckles

For the child to have freckles his genotype must be FF of Ff

Explanation:

Since freckles is dominant (F) and not having freckles is recessive (f), If the child has a genotype with at least one dominant gene (that is FF, Fr) , the child would have freckles but for the child not to have freckles, the genotype gene must both be recessive (that is ff)

Since the other has Ff and a father has Ff, if they have four children, the children genotypes would be FF, Ff, Ff and ff. Since freckles (F) is dominant for the child to have freckles his genotype must be FF of Ff

(newtons first law)

conservation of momentum law states :

momentum before collision = momentum after collision

momentum p (kg-m/s)= mass * velocity

say moving car=1 000 kg, velocity = 10 m/s then p = 1 000*10= 10 000 kg-m/s

say still car = 2 000 kg, velocity = 0 m/s then p = 2 000* 0 = 0 kg-m/s

total momentum prior to collision = 10 000 + 0 = 10 000 kg-m/s

momentum after collision = 10 000 kg-m/s

mass now = 1 000 kg+2 000 kg = 3 000 kg

10 000 = 3 000 kg* velocity m/s

10 000/3 000 = velocity

3.33 m/s = velocity after collision

an impulse is a force applied over time , momentum is exclusive of external forces and a perfect collision is implied