The free fall acceleration due to the Earth's gravity will always be 9.8m/s^2. So, if this question is taking place on Earth, then the acceleration of an object in free fall is 9.8m/^2.
This the correct answer who will know this answer
Given:
Momentum of the dog (p) = 120.5 kg m/s
Speed of the dog (v) = 5 m/s
To Find:
Mass of the dog (m)
Concept/Theory:

- It is defined as the quantity of motion contained in a body.
- It is measured as the product of mass of the body and it's speed.
- It is represented by p.
- It's SI unit is kg m/s
- Mathematical Representation/Equation of Momentum:

Answer:
By using equation of momentum, we get:

Mass of the dog (m) = 24.1 kg
The speed change : Δv = 0.41 m/s
<h3>Further explanation</h3>
Given
mass = 5.5 kg
Force = 15 N
time = 0.15 s
Required
the speed change
Solution
Newton 2nd's law
Impulse and momentum
F = m.a
F = m . Δv/t
F.t = m.Δv
Input the value :
15 N x 0.15 s = 5.5 kg x Δv
Δv = 0.41 m/s
Answer: b
Explanation: the two pieces will repel as both have obtained a static charge.