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3 years ago

When is a body said to be at rest

1 answer:

3 0

rest is the state of a body which is stationary relative to a particular frame of reference or another object. When the state of a body does not changes with time with respect to its surroundings in a particular frame of reference that time it is said to be at rest.

in other words we can say that when a body has zero velocity and its position is not changing with time relative to its surrounding then it is said to be at rest.

For example a chair on which you are sitting is at rest or a table on which your desktop is kept is rest because its position is not changing.

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If you are lying down and stand up quickly, you can get dizzy or feel faint. This is because the blood vessels don't have time t

sammy [17]

Complete Question

If you are lying down and stand up quickly, you can get dizzy or feel faint. This is because the blood vessels don’t have time to expand to compensate for the blood pressure drop. If your brain is 0.4 m higher than your heart when you are standing, how much lower is your blood pressure at your brain than it is at your heart? The density of blood plasma is about 1025 kg/m3 and a typical maximum (systolic) pressure of the blood at the heart is 120 mm of Hg (= 0.16 atm = 16 kP = 1.6 × 104 N/m2).

Answer:

The pressure at the brain is $P_b = 89.872 \ mm \ of \ Hg$

Explanation:

Generally is mathematically denoted as

$P = \rho gh$

Substituting $1025 kg/m^3$ for $\rho$ (the density) , $9.8 m/s^2$ for g (acceleration due to gravity) , 0.4m for h (the height )

We have that the pressure difference between the heart and the brain is

$P = 1025 * 9.8 *0.4$

$= 4018 N/m^2$

But the pressure of blood at the heart is given as

$P_h=120 mm of Hg =$ $120 * 133 = 1.59*10^3Pa$

Now the pressure at the brain is mathematically evaluated as

$P_b = P_h - P$

$= 1.596*10^4 - 4018$

$= 11982 N/m^2$

$P_b= \frac{11982}{133} = 89.872 \ mm \ of \ Hg$

3 0

4 years ago

A snowboarder is sliding back and forth on a half pipe at one point she leaves the top of the half pipe and slides to the other

r-ruslan [8.4K]

Answer:

he kinetic energy increases on the descent, being maximum at the lowest point of the trajectory.

Explanation:

In these semicircular sections the skaters slide from one side to the other, in the downward path their kinetic energy increases and their potential energy decreases; When it leaves the ramp and is in the air, the kinetic energy decreases rapidly, up to the point of maximum height where the kinetic energy is zero.

Consequently, the kinetic energy increases on the descent, being maximum at the lowest point of the trajectory.

3 0

3 years ago

Read 2 more answers

Speedy Sue, que conduce a 30.0 m/s, entra a un túnel de un carril. En seguida observa una camioneta lenta 155 m adelante que se

Romashka [77]

Answer:

Si ocurre una colisión. 5.201 segundos después de que Speedy Sue ingrese al túnel y a una distancia de 128.995 metros.

Explanation:

Supongamos que el vehículo de Speedy Sue decelera a razón constante, mientras que la camioneta se desplaza a velocidad constante. Se requiere conocer si ambos vehículos colisionarán, lo cual implica conocer si existe algún instante tal que ambos tengan la misma posición. Consideremos además que la posición de referencia se encuentra en la posición inicial de Sppedy Sue. Entonces, las ecuaciones cinemáticas son:

Speedy Sue

$x_{S} = x_{S,o}+v_{S,o}\cdot t+\frac{1}{2}\cdot a_{S}\cdot t^{2}$

Camioneta lenta

$x_{C} = x_{C,o} +v_{C}\cdot t$

Donde:

$x_{S,o}$ , $x_{C,o}$ - Posiciones iniciales de Speedy Sue y la camioneta lenta, medidas en metros.

$v_{S,o}$ - Velocidad inicial de Speedy Sue, medida en metros por segundo.

$v_{S}, v_{C}$ - Velocidades actuales de Speedy Sue y la camioneta lenta, medidas en metros por segundo.

$a_{S}$ - Deceleración de Speedy Sue, medida en metros por segundo cuadrado.

$t$ - Tiempo, medido en segundos.

Si conocemos que $x_{S} = x_{C}$ , $x_{S,o} = 0\,m$ , $x_{C,o} = 155\,m$ , $v_{S,o} = 30\,\frac{m}{s}$ , $v_{C} =-5\,\frac{m}{s}$ y $a_{S} = -2\,\frac{m}{s^{2}}$ , encontramos la siguiente función cuadrática:

$155\,m + \left(-5\,\frac{m}{s} \right)\cdot t = 0\,m+\left(30\,\frac{m}{s} \right)\cdot t +\frac{1}{2}\cdot (-2\,\frac{m}{s^{2}} )\cdot t^{2}$

$-t^{2}+35\cdot t-155 = 0$ (Ec. 1)

Las raíces de esta función son:

$t_{1}\approx 29.798\,s$ , $t_{2} \approx 5.201\,s$

La colisión ocurriría en la raíz positiva más pequeña, es decir:

$t \approx 5.201\,s$

Ahora, la posición en que ocurriría la colisión se determina a partir de la ecuación de desplazamiento de la camioneta lenta, es decir: ( $v_{C,o} = -5\,\frac{m}{s}$ , $x_{C,o} = 155\,m$ , $t \approx 5.201\,s$ )

$x_{C} = 155\,m +\left(-5\,\frac{m}{s}\right)\cdot (5.201\,s)$

$x_{C} = 128.995\,m$

En síntesis, si ocurre una colisión. 5.201 segundos después de que Speedy Sue ingrese al túnel y a una distancia de 128.995 metros.

0 0

3 years ago

What is the momentum of a bicycle with a mass of 18 kg traveling at 20 m/s?

iogann1982 [59]

Answer:360 kg m/s

Explanation:Momentum refers to an object's quantity of motion.

Formula for Momentum: p=mv

p = refers to the momentum

m = refers to the object's mass (this is represented by the unit kg or kilogram)

v = this refers to the object's velocity (this is represented by the unit m/s or meter per second)

So, given that the bike has a mass of 18 kg and is traveling at 20 m/s, then you can already get the momentum by multiplying both of these values.

p = the bike's momentum (what is being asked here)

m = 18 kg

v = 20 m/s

Thus, p = 18kg × 20 m/s = 360 kg m/s

The bike's momentum is 360 kg m/s.

Brainlist please

6 0

3 years ago

An undiscovered planet, many lightyears from Earth, has one moon in a periodic orbit. This moon takes 2060 × 103 seconds (about

Fittoniya [83]

Answer:

Acceleration, $a=2.22\times 10^{-3}\ m/s^2$