The answer is 2. by transforming energy into other forms
This question is off-base and misleading from the beginning.
When you jump off the Earth, your momentum changes, <em>and the Earth moves away from you with an equal change of momentum in the opposite direction</em>.
1). Momentum is conserved when you jump. But we don't feel the Earth moving. Since the Earth's mass is a bazillion times greater than YOUR mass, the speed with which the Earth moves away from you is only one bazillionth of your speed. That way, the product of (mass) x (speed) is the SAME for you and for the Earth, and momentum is conserved.
2). <em>Of course !</em> If everyone jumped at the same time, the Earth's momentum would change. In answer-(1), I explained that the Earth's momentum changes whenever <em>ONE PERSON</em> jumps. So 7 billion people all jumping at the same time would certainly make it change.
Answer:
350 N/m
Explanation:
If we are assuming the stretch does not exceed the elastic range of the material, then by Hooke's law the spring constant of the cord is simply the ratio between the force 70N acting on the cord to stretch 20cm or 0.2m
k = 70 / 0.2 = 350 N/m
The spring constant is 350 N/m
Equal to 50
law of reflection: angle of incidence equals angle of reflection
