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3 years ago

Please help will give the brainliest How did humans decide how long a year should be?

Physics

2 answers:

worty [1.4K]3 years ago

5 0

Answer:

The decided by staring at and observing the stars.

Explanation:

scZoUnD [109]3 years ago

3 0

By how long the earth takes to orbit the sun just once. also including the geocentric model.

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Two identical billiard balls are rolling toward each other at the same speed. What will be true after they collide head–on?

ioda

My guess is either they come to a stop when they come in contact, or one ball is going to go the opposite direction.

3 0

3 years ago

Read 2 more answers

Adolf and Ed are wearing harnesses and are hanging at rest from the ceiling by means of ropes attached to them. Face to face, th

exis [7]

Answer:

0.78 m

Explanation:

By the conservation of energy, the energy that they gain from potential energy, must be equal to the kinetic energy. So, for Adolf:

Ep = Ek

ma*g*ha = ma*va²/2

Where ma is the mass of Adolf, g is the gravity acceleration (10 m/s²), ha is the height that he reached, and va is the velocity. So:

100*10*0.51 = 100*va²/2

50va² = 510

va² = 10.2

va = √10.2

va = 3.20 m/s

Before the push, both of them are in rest, so the momentum must be 0. The system is conservative, so the momentum after the push must be equal to the momentum before the push:

ma*va + me*ve = 0, where me and ve are the mass and velocity of Ed. So:

100*3.20 + 81ve = 0

81ve = 320

ve = 3.95 m/s

By the conservation of energy for Ed:

me*g*he = me*ve²/2

81*10*he = 81*(3.95)²/2

810he = 631.90

he = 0.78 m

5 0

3 years ago

Supposing you were in space..in a weightless environment, would it require a force to set an object in motion? Explain..

Dvinal [7]

Answer:

Yes, a force is require to set an object in motion.

Explanation:

In space, even if you feel weightless, you are subject to motion. If you are orbiting the Earth, you are under the constant influence of Earth having a free-fall acceleration equal to the centripetal acceleration.
To disturb this orbital motion, an external force is required.
According to Newton's laws of motion, a force is required to change the state of the rest of a body or to change the velocity or direction if it is moving with uniform velocity along a straight line.
Whenever there is a change in velocity or direction of a body there is a force acting on it.

8 0

3 years ago

Consult Multiple-Concept Example 5 for insight into solving this problem. A skier slides horizontally along the snow for a dista

antoniya [11.8K]

The initial velocity of the skier is 4.5 m/s

Explanation:

There is only one force acting on the skier in the horizontal direction, and it is the force of friction, whose magnitude is

$F_f = -\mu_k mg$

where

$\mu_k = 0.050$ is the coefficient of kinetic friction

m is the mass of the skier

$g=9.8 m/s^2$ is the acceleration of gravity

The negative sign is due to the fact that the direction of the force of friction is opposite to the direction of motion of the skier.

According to Newton's second law, the net force acting on the skier is equal to the product between his mass and his acceleration, so we can write:

$F=ma\\ \rightarrow -\mu_k mg = ma$

So, the acceleration of the skier is

$a=-\mu_k g$

Now we can apply the following suvat equation to find the initial velocity of the skier:

$v^2-u^2=2as$

where

v = 0 is the final velocity (he comes to a stop)

u is the initial velocity

s = 21 m is the displacement

a is the acceleration

Substituting the equation for the acceleration and solving for u, we find

$u=\sqrt{v^2-2as}=\sqrt{-2(-\mu_k g) s}=\sqrt{2(0.050)(9.8)(21)}=4.5 m/s$

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5 0

3 years ago

Starting from rest, you pushed a 10.0 kg lawnmower a distance of 25 meters by applying a force of 75 N at an angle 35 degrees be

irga5000 [103]

The lawn mower is moving with a velocity of 17.53 m/s

<h3>Definition of Energy and Work </h3>

Energy is the ability to do work while Work is defined as the product of force and distance moved in the direction of the force. Both work and energy are measured in Joule (J)

Work = Force (F) × distance (d) = FdCosθ

With the above formula, we can obtain the energy used in pushing the lawn mower as illustrated below

From the question given above, the following data were obtained:

•Force (F) = 75 N

•Distance (d) = 25 m

•Angle (θ) = 35°

•Energy (E) =?

E = FdCosθ

E = 75 × 25 × Cos 35

E = 1535.91 J

<h3>Definition and Determination of the velocity</h3>

Velocity is the rate of change of displacement with time.

Velocity and energy are related according to the following equation:

E = ½ × mass (m) × square velocity (v²)

E = ½mv²

With the above formula, we can obtain the velocity of the lawn mower as follow

•Mass (m) = 10 Kg

•Energy (E) = 1535.91 J

•Velocity (v) =?

E = ½mv²

1535.91 = ½ × 10 × v²

1535.91 = 5 × v²

Divide both side by 5

v² = 1535.91 / 5

Take the square root of both side

v = √(1535.91 / 5)

v = 17.53 m/s

Thus, the lawn mower is moving with a velocity of 17.53 m/s

<h3 />

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4 0

3 years ago