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3 years ago

I AM GIVING 95POINTS HELP PLEASE!!

Physics

2 answers:

ValentinkaMS [17]3 years ago

4 0

This is a fun question - your science teacher is creative!

First is easy, 25000 feet converts to 7620 meters

Potential energy is a product of mass, gravity and height. In this case, mass is 90Kg and height is 7620m. gravity on earth is 9.8m/s2.

Potential energy = 90(9.8)(7620) = 6720840J

By Newton 2nd law, force is equal to mass times acceleration.

Gravity force = mass*gravity

= 90(9.8) = 882N

Acceleration when he leaves the plane is gravity, 9.8m/s2

With no wind resistance, the acceleration is constant at 9.8.

Using kinematic equation, v2 = u2 + 2as where u is initial velocity, v is final velocity, a is acceleration and s is distance traveled.

In this case, u=0, a=9.8, s=7620

v^2 = 2(9.8)(762) = 149352

final velocity = sqrt (149352) = 386.5m/s

150MPH converts to 67m/s.

If he is falling at a constant speed of 150MPH, then he is not accelerating.

As he is not accelerating, the net force = gravity force - wind resistance = 0

wind resistance = gravity force

= 90(9.8) = 882N

If there is no wind resistance, by conservation of energy,

final Kinetic Energy = initial Potential energy

= mass * gravity * height

= 90*9.81*7620

= 6720840J

He is unhurt because the safety net provides a soft landing. It decelerates his momentum gradually over time to avoid injury.

Firlakuza [10]3 years ago

3 0

25,000 Feet = 7620m

PE = mgh where m is mass, g is gravity accel: 9.8 n h is height

= 90 x 9.8 x 7620

= 6720840J

= 6.72MJ

F = ma where m is mass, a is accel = gravity = 9.8

= 90 x 9.8

= 882N

Accel = gravity = 9.8m/s^2

KE = 1/2mv^2 where m is mass n v is vel

if no wind resistance, PE leaving airplane = KE at net

6720840 = 1/2 x 90 x v^2

v^2 = 149352

v = 386.5m/s

150MPH=67m/s

@150MPH, his speed is not changing so accel=0

accel=0, force=0 by newton's second law

force=0 when wind resistance = gravity = 9.8m/s^2

by conservation of energy, Luke's KE = PE = mgh = 6720840J

he was unhurt cuz' his momentum was absorbed by the net

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3 years ago

According to Darwin's theory of evolution, how does natural selection cause species to evolve over time?

Elena L [17]

As time goes on, members of a population with favorable traits continue to breed while those without these traits eventually die off. For instance, if all of the food in an area was high up in the trees, only members of the species with long necks are able to eat and continue to live and reproduce. Those with shorter necks will not be able to eat and will eventually die off. Over time, the species will evolve to have long necks.

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4 0

3 years ago

acontainer is filled whith mercury to alevel of 10m whit water to alevel of 8m and whit oil to alevel of 5m the densities oil ,w

Alborosie

Answer:

1450.4 KN $m^{2}$

Explanation:

Pressure = ρhg

where: ρ is the density of the liquid, h is the height and g the force of gravity.

Total pressure exerted by the liquids at the base = Pressure of oil + Pressure of water + Pressure of mercury

So that,

i. Pressure of oil = ρhg

(ρ = 0.8 g/cm³ = 800 kg/m³)

= 800 x 5 x 9.8

= 39200

Pressure of oil = 39200 N $m^{2}$

ii. Pressure of water = ρhg

(ρ = 1 g/cm³ = 1000 kg/m³)

= 1000 x 8 x 9.8

= 78400

Pressure of water = 78400 N $m^{2}$

ii. Pressure of mercury = ρhg

(ρ = 13.6 g/cm³ = 13600 kg/m³)

= 13600 x 10 x 9.8

= 1332800

Pressure of mercury = 1332800 N $m^{2}$

So that,

Total pressure exerted by the liquids at the base = 39200 + 78400 + 1332800

= 1450400

= 1450.4 KN $m^{2}$

Total pressure exerted by the liquids at the base is 1450.4 KN $m^{2}$ .

8 0

3 years ago

Can work be done on a system if there is no motion?

Minchanka [31]

Answer:

D) No, because of the way work is defined

Explanation:

The work done on an object is given by:

$W=Fd cos \theta$

where

F is the force applied on the object

d is the displacement of the object

$\theta$ is the angle between the direction of the force and the displacement

From the formula, we observe that if there is no motion involved, then the displacement of the object is zero:

d = 0

As a result, the product in the formula is also zero, therefore the work done will be zero as well.

5 0

3 years ago

A car moving with an initial speed of 25 m/s slows down to a speed of 5 m/s in 10 seconds Calculate a) the acceleration of the c

stealth61 [152]

Answer :

(a) The acceleration of the car is, $-2m/s^2$

(b) The distance covered by the car is, 150 m

Explanation :

By the 1st equation of motion,

$v=u+at$ ...........(1)

where,

v = final velocity = 5 m/s

u = initial velocity = 25 m/s

t = time = 10 s

a = acceleration of the car = ?

Now put all the given values in the above equation 1, we get:

$5m/s=25m/s+a\times (10s)$

$a=-2m/s^2$

The acceleration of the car is, $-2m/s^2$

By the 2nd equation of motion,

$s=ut+\frac{1}{2}at^2$ ...........(2)

where,

s = distance covered by the car = ?

u = initial velocity = 25 m/s

t = time = 10 s

a = acceleration of the car = $-2m/s^2$

Now put all the given values in the above equation 2, we get:

$s=(25m/s)\times (10s)+\frac{1}{2}\times (-2m/s^2)\times (10s)^2$

By solving the term, we get:

$s=150m$

The distance covered by the car is, 150 m

8 0

3 years ago