The change in velocity from 30 m/s north to 40 m/s south is a change of 70 m/s south
Answer:

Explanation:
We have the following data:
- distance covered by the child: d = 2 m (length of the slide)
- time taken to cover this distance: t = 3 s
- initial velocity of the child: 0 m/s (he starts from rest)
So we can find the acceleration by using the equation:

Where a is the acceleration.
Substituting the values and solving for a,

Answer:
The answer is D. A Vacumn
Explanation:
Sound cannot travel through a vacuum. A vacuum is an area without any air, like space. So sound cannot travel through space because there is no matter for the vibrations to work in.
That's a weird graph, but judging from the units the acceleration is the slope of the graph.
a = (0.8 - 0.3)/(0.16 - 0.055) = 4.76 m/s²
For any mass m:
a = F/m
v = √2*F/m*s = √2F/sm = k/√m
Momentum = mv = k√m
Energy = 1/ mv² = 1/2 m.k²/m = 1/2k²
SO
Both will have same energy
The larger mass will have greater momentum