The train travells at he speed of 225 km/2.5h
now
225km=225000m
2.5 hr=150min=9000s
=>avg sp of train is=225000/9000s=25m/s
I believe it's DNA.
Here're some sentences to explain:
Genetic material, also known as deoxyribonucleic acid<span> (</span>DNA<span>) and </span>Ribonucleic acid<span> (</span>RNA<span>), plays a fundamental role in the composition of living organisms.</span>
Hi Spycn2115
Newton's first law states that objects in motion stay in motion until an unbalanced force is acted upon it is a good fact. When I first personally heard of it in class I had no clue but when I researched it I learned that one good example of this would be those cradle balls and if u swing it, it will keep constantly hitting each other back and fourth over and over until someone grabs it and stops it, so that's what objects in motion stays in motion until an unbalanced force is acted upon it means, because the balls are in motion by moving left to right constantly and its staying in motion by not stopping and that unbalanced force is someone or something maybe hitting it or knocking it over could stop it, balanced means staying still and equal, unbalanced means unstill so moving, the cradle balls are KE and PE, (Kinect and potential energy) because kinetic means moving, so the balls are moving, and potential means stored up, so before u even swing u have the potential energy to swing it different ways before it becomes kinetic. That's one of my favorite examples of Newton's first law and I left you a pic below of cradle balls to help you get the idea.

Answer:
(a) 
(b) 
Explanation:
According to Newton's second law:

Recall that the frictional force is related jointly with the coefficient of friction and normal force
. Replacing in the above equation, we get the coefficient of friction:

(a) The coefficient of static friction is related with the force required to set the block in motion:

(b) The coefficient of kinetic friction is related with the force required to keep the block moving with constant speed:
