Where does the rest of the energy 90% go?

A 62-kg person jumps from a window to a fire net 20.0 m directly below, which stretches the net 1.4 m. Assume that the net behav

gayaneshka [121]

Answer:

a) x = 0.098

b) x = 2.72 m

Explanation:

(a) To find the stretch of the fire net when the same person is lying in it, you can assume that the net is like a spring with constant spring k. It is necessary to find k.

When the person is falling down he acquires a kinetic energy K, this energy is equal to the elastic potential energy of the net when it is max stretched.

Then, you have:

$K=U\\\\\frac{1}{2}mv^2=\frac{1}{2}kx^2$ (1)

m: mass of the person = 62kg

k: spring constant = ?

v: velocity of the person just when he touches the fire net = ?

x: elongation of the fire net = 1.4 m

Before the calculation of the spring constant, you calculate the final velocity of the person by using the following formula:

$v^2=v_o^2+2gy$

vo: initial velocity = 0 m/s

g: gravitational acceleration = 9.8 m/s^2

y: height from the person jumps = 20.0m

$v=\sqrt{2gy}=\sqrt{2(9.8m/s^2)(20.0m)}=14\frac{m}{s}$

With this value you can find the spring constant k from the equation (1):

$mv^2=kx^2\\\\k=\frac{mv^2}{x^2}=\frac{(62kg)(14m/s)^2}{(1.4m)^2}=6200\frac{N}{m}$

When the person is lying on the fire net the weight of the person is equal to the elastic force of the fire net:

$W=F_e\\\\mg=kx$

you solve the last expression for x:

$x=\frac{mg}{k}=\frac{(62kg)(9.8m/s^2)}{6200N/m}=0.098m$

When the person is lying on the fire net the elongation of the fire net is 0.098m

b) To find how much would the net stretch, If the person jumps from 38 m, you first calculate the final velocity of the person again:

$v=\sqrt{2gy}=\sqrt{2(9.8m/s^2)(38m)}=27.29\frac{m}{s}$

Next, you calculate x from the equation (1):

$x=\sqrt{\frac{mv^2}{k}}=\sqrt{\frac{(62kg)(27.29m/s)^2}{6200N/m}}\\\\x=2.72m$

The net fire is stretched 2.72 m

5 0

2 years ago

2. Above right: The four positions of the thrown ball with no gravity are

padilas [110]

The characteristics of the projectile launch allows to find the results for the questions about the movement of the ball are:

In the attached we see the vertical speed decreases with height and the curve is of the parabolic type.

In the movement is several dimensions, each one is independent of the others, the movement in the x axis does not affect the movement in the y axis.

Kinematics studies the motion of bodies looking for relationships between position, velocity and acceleration. In the case of vertical and projectiles launch the acceleration on the vertical axis is the acceleration of gravity directed downward.

In the attachment we can see the position of the ball for two distances in the case of projectile launching.

We can see that the speed of the ball decreases with height according to the relation

y = go t - ½ g t²

Where y is the height, g is the initial vertical velocity, g is the acceleration of gravity and t is time.

In all movements in various dimensions we assume that each movement in an . axis is independent

In the case of projectile launching, on the vertical axis there is an acceleration of gravity and on the horizontal axis there is no acceleration, the only parameter that this gives the two movements is the time, which is a scalar.

In conclusion, using the characteristics of the projectile launch, we can find the results for the questions about the movement of the ball are:

In the movement is several dimensions, each one is independent of the others, the movement in the x axis does not affect the movement in the y axis.

In the attached we see the vertical speed decreases with height and the curve is of the parabolic type.

Learn more about projectile launch here: brainly.com/question/24888457

4 0

2 years ago

What changes dead plants and animals into ammonia compounds?

lapo4ka [179]

Nitrogen fixing bacteria changes dead plants and animals into ammonia compounds.

<h2>What is nitrogen fixation?</h2>

Atmospheric nitrogen is converted into nitrogen oxides by the action of lightning, which helps its incorporation into the soil.

<h3>Characteristics of Nitrogen fixing bacteria</h3>

Nitrogen is fixed by these bacteria and other prokaryotes through various metabolic processes, which convert it into different usable compounds, such as ammonia (NH3) and ammonium ion (NH4+).

These microorganisms can be found in soil and water, or as plant symbionts.

Therefore, we can conclude that nitrogen fixing bacteria fix nitrogen from the air, that is, they originate soluble compounds by plants, such as ammonia.

Learn more about nitrogen fixation here: brainly.com/question/14726009

7 0

1 year ago

the kinetic energy of an object with mass m moving with a velocity of 5 m/s is 25 j what will be its kinetic energy when its vel

Dmitriy789 [7]

Answer:

100 J, 225 J

Explanation:

The kinetic energy of an object is given by:

$K=\frac{1}{2}mv^2$

where

m is the mass of the object

v is the velocity of the object

In this problem, the initial kinetic energy of the object is

K = 25 J

Then, the velocity is doubled, which means

v' = 2v

Therefore, the new kinetic energy will be

$K'=\frac{1}{2}m(2v)^2 = 4(\frac{1}{2}mv^2)=4K$

Therefore, the kinetic energy has quadrupled:

$K' = 4(25)=100 J$

Later, the velocity is tripled, which means

v'' = 3v

Therefore, the new kinetic energy will be

$K''=\frac{1}{2}m(3v)^2 = 9(\frac{1}{2}mv^2)=9K$

Therefore, the kinetic energy has increased by a factor of 9:

$K' = 9(25)=225 J$

4 0

3 years ago

A power supply has an open-circuit voltage of 40.0 V and an internal resistance of 2.00 V. It is used to charge two storage batt

Natali [406]

Complete Question

A power supply has an open-circuit voltage of 40.0 V and an internal resistance of 2.00 $\Omega$ . It is used to charge two storage batteries connected in series, each having an emf of 6.00 V and internal resistance of 0.300 $\Omega$ . If the charging current is to be 4.00 A, (a) what additional resistance should be added in series? At what rate does the internal energy increase in (b) the supply, (c) in the batteries, and (d) in the added series resistance? (e) At what rate does the chemical energy increase in the batteries?