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3 years ago

Why do scientist study fossils?

1 answer:

8 0

Scientists study fossils of plants, animals, and other organisms in order to better understand what life was like on Earth many years ago and how it has changed over time. Fossils are important evidence for the theory of evolution.

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A luggage handler pulls a 20.0 kg suitcase up a ramp inclined at 25 degrees above the horizontal by a force F of magnitude 145 N

Nonamiya [84]

Answer:

A) 667 J

B) 381.4 J

C) 0 J

D) 245.4 J

E) 40.2J

F) 2 m/s

Explanation:

Let g = 9.81 m/s2

A) The work done on the suitcase is the product of the force applied and the distance travelled:

w = Fs = 145 * 4.6 = 667 J

B) The work done by gravitational force the dot product between the gravity vector and the distance vector

$W_g = \vec{P}\vec{s} = mgs sin\alpha = 20*9.81*4.6*sin25^o = 381.4 J$

C) As the normal force vector is perpendicular to the distance vector, the work done by the normal force is 0

D) The work done on the suitcase by friction force is the product of the force applied and the distance travelled, whereas friction force is the product of normal force and coefficient

$W_f = F_fs = \mu N s = \mu s mgcos\alpha = 0.3* 4.6 * 20*9.81*cos25^o = 245.4 J$

E) The total workdone on the suite case would be the pulling work subtracted by gravity work and friction work

$W = w – W_g – W_f = 667 – 381.4 – 245.4 = 40.2 J$

F) As the suit case has 0 kinetic and potential energy at the bottom, and the total work done is converted to kinetic energy at 4.6 m along the ramp, we can conclude that:

$E_k = W = 40.2 j$

$mv^2/2 = 40.2$

$20v^2/2 = 40.2$

$10v^2 = 40.2$

$v^2 = 4.02$

$v = \sqrt{4.02} = 2 m/s$

3 0

3 years ago

Air is flowing through a rocket nozzle. Inside the rocket the air has a density of 5.25 kg/m3 and a speed of 1.20 m/s. The inter

Dafna1 [17]

Answer:

The velocity at exit of the nozzle is 175.8 m/s

Solution:

As per the question:

Air density inside the rocket, $\rho_{i} = 5.25\ kg/m^{3}$

Speed, v = 1.20 m/s

The inner diameter of the rocket, $d_{i} = 15.0\ cm = 0.15\ m$

The inner radius of the rocket, $r_{i} = \frac{0.15}{2} = 0.075\ m$

The exit diameter of the nozzle, $d_{e} = 2.50\ cm = 0.025\ m$

The exit radius of the nozzle, $r_{e} = 0.0125\ m$

Air density inside the nozzle, $\rho_{n} = 1.29\kg/m^{3}$

Now,

To calculate the air speed when it leaves the nozzle:

Mass rate in the interior of the rocket, $\frac{dM}{dt} = \rho_{i}Av$

Mass rate in the outlet of the nozzle, $\frac{dm}{dt} = \rho_{n}A'v'$

Now,

$A = \rho_{i}r_{i}^{2}$

Now,

We know that:

$Av = A'v'$

$\rho_{i}r_{i}^{2}v = \rho_{n}r_{e}^{2}v'$

$5.25\times 0.075^{2}\times 1.2 = 1.29\times 0.0125^{2}v'$

v' = 175.8 m/s

7 0

3 years ago

PLEASE HELP ME WITH THIS

Kitty [74]

Answer:

i think it might be c but i know its not A or B and im

on the fence for D so the best answer would be C

Explanation:

3 0

3 years ago

Write any two important of gravitational force?

eimsori [14]

Answer:

Explanation:

Gravitational force is important because:

1. because of the gravitational force of the earth, the atmosphere is present around its surface, which is crucial for sustainability of life on earth

2. we are able to perform motion due to the force of gravity

5 0

3 years ago

PLEASE HELP ME I AM TIMED!

Crank

Answer:

violet has the highest frequency

Explanation:

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3 years ago