Newton Question?

Question

When a dog gets wet, it shakes its body from head to tail to shed the water. Explain, in terms of Newton?s first law, why this works.

Answer 1

Ok, a dog shakes to the left, the water starts moving left towards the end of his fur, then the dog shakes right. The Fur, being attached to the dog, moves right, the water however continued moving left because of it's momentum.

Do this a few times and most of the water is gone. . .

Answer 2

The dog's shaking is like rotating something...it creates centripetal/centrifugal forces acting along the radii of that shaking action. Thus, the water is sprayed all over the living room by F = mv^2/r, where m = mass of each water droplet, v = the tangential velocity of the hair on the shaking dog, and r = the distance of each drop from the center of the shake (i.e. the dog's backbone). This is a form of F = ma; where a along the radii is = v^2/r. This is Newt's second law, by the way, which I think is more interesting than his first law.

Newt's first law, that mass will continue moving in a straight path or will continue to stay at rest unless a change force is applied to the mass, means that the launched droplets will not travel a straight line because they are continually acted on by the force of gravity = W = mg and drag forces by the air; where W is the force of gravity (aka weight) on each droplet of mass m under a gravitational acceleration g = 9.81 m/sec^2 on Earth's surface. We are fortunate to have W and the drag forces; othewise, the water would get all over the walls as well as the floor.

Answer 3

If the apple analogy is true about Newton's gravity, why not a wet dog shaking off his water and soaking Newton for his motion formulas?

Once the water is in motion, it will continue until it is acted upon by an opposing force - and the quick shake in the other direction will assure that it continues right off the dog and into the air!

Answer 4

After the dog gives the water motion by shaking, the water tends to stay in uniform motion until something else acts upon it. Thus the water will keep moving away from the dog until it falls to the ground due to the earth's gravity and a little bit of air friction.

Answer 5

it works on newtons first law: everything remain in its rest or in motion unless another unbalanced for acts upon it, which is also termed as inertia .
so when the dog shakes it body the water keeps itself in its rest position whereas the body moves suddenly which makes the water to shed.

we can also take example of a vehicle while we are driving car at great speed and when we suddenly brake we are jerked forward cause of newtons 1st law

Answer 6

Well when the water trapped on the dogs fur,is shaken .off.This water realised to atmosphere by vigorous shaking becomes subject to gravitation.Just like rain