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3 years ago

15

El sargento Conejero toma el sol en su colchoneta, de 2 m2 de superficie, flotando en el agua de la piscina (d = 1 g/cm3 ). Si o

bservamos que ésta se hunde 2,7 cm, ¿cuál es el peso del sargento? (Desprecia el peso de la colchoneta).

1 answer:

galben [10]3 years ago

7 0

Answer:

W = 529.2 N

Explanation:

We can solve this problem using the translational equilibrium equation, where the forces are the weight of the sergeant and the thrust of the water given by Archimedes' principle

B - W = 0

where the thrust is

B = ρ g V_liquid

The volume of the displaced liquid is

V = A h

we substitute

ρ g A h = W

We reduce the magnitudes to the SI system

h = 2.7 cm = 0.027 m

ρ = 1 g / cm3 = 1000 kg / m³

let's calculate

W = 1000 9.8 2 0.027

W = 529.2 N

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A 45 kg object has a momentum of 225 kg-m/s northward. What is the object's velocity?

melomori [17]

Answer: 5 m/s North

Explanation:

Velocity = Momentum/Mass

Velocity = 225 kg*m/s/45kg

Velocity = 5 m/s North

3 0

2 years ago

At the beach in San Francisco (0 meters) the pressure of the atmosphere is 101.325 kPa

Korvikt [17]

Answer:

$P = -\frac{17978}{1609344}(h)+101.325$

Explanation:

Given

$h = height$

$P = Pressure$

$(h_1,P_1) = (0,101.325)$

$(h_2,P_2) = (1609.344 ,83.437 )$

Required

Determine the linear equation for P in terms of h

First, we calculate the slope/rate (m);

The following formula is used:

$m = \frac{P_2 - P_1}{h_2 - h_1}$

Substitute values for P's and h's

$m = \frac{83.347 - 101.325}{1609.344- 0}$

$m = \frac{-17.978}{1609.344}$

$m = -\frac{17.978}{1609.344}$

Multiply by 1000/1000

$m = -\frac{17.978 * 1000}{1609.344*1000}$

$m = -\frac{17978}{1609344}$

The equation is then calculated using:

$P - P_1 = m(h - h_1)$

Substitute values for m, h1 and P1

$P - P_1 = m(h - h_1)$

$P - 101.325 = -\frac{17978}{1609344}(h - 0)$

$P - 101.325 = -\frac{17978}{1609344}(h)$

Make P the subject

$P = -\frac{17978}{1609344}(h)+101.325$

<em>The above is the required linear equation</em>

8 0

3 years ago

A 0.030 kg lead bullet hits a steel plate, both initially at 20?C. The bullet melts and splatters on impact. Assume that 80% of

Dmitry_Shevchenko [17]

Answer:

(a). The required is 1871.2 J.

(b). The speed the lead bullet is 395 m/s.

(c). The 20% of energy must have gone into collision between steel plate and bullet.

Explanation:

Given that,

Mass of bullet = 0.030 kg

Temperature = 20°C

(a). We need to heat required to increase the temperature of the lead bullet and melt it

Using formula of heat

$Q=mS\Delta T+mL$

Where, m = mass of lead bullet

S = specific heat

L = latent heat

T = Temperature

Put the value into the formula

$Q=0.030\times130\times(327.5-20)+0.030\times22400$

$Q=1871.2\ J$

The required is 1871.2 J.

(b). Assume that 80% of the bullet’s kinetic energy goes into increasing its temperature and then melting it

We need to calculate the energy

$Q=\dfrac{1871.2}{0.8}$

$Q=2339 J$

We need to calculate the speed the lead bullet

Using formula of speed

$K.E=Q$

$\dfrac{1}{2}mv^2=2339$

$v^2=\dfrac{2339\times2}{0.030}$

$v=\sqrt{\dfrac{2339\times2}{0.030}}$

$v=394.8 = 395\ m/s$

The speed the lead bullet is 395 m/s.

(c). The 20% of energy must have gone into collision between steel plate and bullet.

Hence, This is the required solution.

6 0

3 years ago

Does an athlete do work on a trophy as she lifts it overhead

bogdanovich [222]

No she/he is doing work for her muscles

3 0

3 years ago

Which factor (s) have the most affect a person’s vital capacity? Rank in order from MOST effect (1) to least effect (5)

jenyasd209 [6]

The factors that affect vital capacity are :

Age
Sex
Height
Body mass
Ethnicity

Explanation:

Vital capacity is the maximum amount of air that a person can exhale once he has filled his lungs with maximum air. So, it is like maximum exhalation after maximum inhalation by a person.

Vital capacity is also equal to Forced Vital Capacity.

Lung usually have their maximum capacity in early adult days and this capacity reduces as the person grows older. So age is the prime factor in this.

A female with same age and height as that of male will have 10-12% less vital capacity than him. So sex is another reason which determines vital capacity.

Person with more height has more vital capacity. This is because lungs capacity is closely related to the third power of person's height.

Person suffering from obesity will have compressed diaphragm, lung and chest cavity , so their vital capacity will be less. So we can say body mass affects vital capacity.

Last factor, ethnicity, is yet to be understood clearly as there is not much evidence of this.

3 0

3 years ago