Answer:1. A chair leaning on a wall
Explanation:
Answer:
low powered radio frequency (RF) energy
Answer:
F=248.5W N
Explanation:
Newton's 2nd Law tells us that F=ma. We will use their averages always. The average acceleration the tennis ball experimented is, by definition:

Since we start counting at 0s and the ball departs from rest, this is just 
So we can write:

Where in the last step we have just multiplied and divided by g, the acceleration of gravity. This allows us to introduce the weight of the ball W since W=gm, so we have:

Substituting our values:

Where the average force exerted has been written it terms of the tennis ball's weight W.
I’m not sure but I think it’s D because we don’t have 20,000 years to make observations
Answer:
a teeter-toter, a car jack and a crowbar