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I am Lyosha [343]

3 years ago

13

superman lived on another planet where the acceleration due to gravity is 23.6 m/s^2. if a woman falls from a building that is 6

5m tall, how long he have to save her before she hits the ground

1 answer:

Anastasy [175]3 years ago

7 0

2,35 seconds before she hits the ground

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An insulated Thermos contains 140 cm3 of hot coffee at 85.0°C. You put in a 15.0 g ice cube at its melting point to cool the cof

Pavel [41]

Answer:

$T = 69^o C$

Explanation:

Here at thermal equilibrium we can say that thermal energy given by Hot coffee is equal to the thermal energy absorbed by ice cubes

So here we have

$Q_{ice} = Q_{coffee}$

now since ice cubes are added into coffee when it is at melting temperature

So here we can say that final temperature of coffee is T degree C

Now we have

$m_1L + m_1c_1\Delta T_1 = m_2c_2\Delta T_2$

here we have

$m_1 = 15 gram$

L = 333 kJ/kg = 333 J/g[/tex]

$c_1 = c_2 = 4186 J/kg C = 4.186 J/g C$

$\Delta T_1 = T - 0$

$\Delta T_2 = 85 - T$

now we have

$15(333) + 15(4.186)(T - 0) = 140(4.186)(85 - T)$

$4995 + 62.79T = 49813.4 - 586.04T$

$648.83 T = 44818.4$

$T = 69^o C$

6 0

3 years ago

A person who weighs 800N on the earth's surface will weigh 200N at what height above the earth

Marina86 [1]

Answer: 6,400 km

Explanation:

The weight of a person is given by:

$W=mg$

where m is the mass of the person and g is the acceleration due to gravity. While the mass does not depend on the height above the surface, the value of g does, following the formula:

$g=\frac{GM}{r^2}$

where

G is the gravitational constant

M is the Earth's mass

r is the distance of the person from the Earth's center

The problem says that the person weighs 800 N at the Earth's surface, so when r=R (Earth's radius):

$800 N= W=mg=m \frac{GM}{R^2}$ (1)

Now we want to find the height h above the surface at which the weight of the man is 200 N:

$200 N = W' = mg' = m \frac{GM}{(R+h)^2}$ (2)

If we divide eq.(1) by eq.(2), we get

$\frac{800 N}{200 N}=\frac{W}{W'}=\frac{(R+h)^2}{R^2}$

$4=\frac{(R+h)^2}{R^2}$

By solving the equation, we find:

$4R^2 = (R+h)^2=R^2+2Rh+h^2\\h^2 +2Rh-3R^2 =0$

which has two solutions:

$h=-3R$ --> negative solution, we can ignore it

$h=R$ --> this is our solution

Since the Earth's radius is $R=6.4\cdot 10^6 m$ , the person should be at $h=R=6.4\cdot 10^6 m=6400 km$ above Earth's surface.

5 0

4 years ago

A bicycle is parked at the top of a hill. What form of energy does it possess?

Anna007 [38]

Answer:

potential.

Explanation:

please mark me brainliest and follow me and also give me a thanks.

8 0

4 years ago

Resistance to the motion of an automobile consists of road friction, which is almost independent of speed, and air drag, which i

Troyanec [42]

Answer:

73.52983 Hp

Explanation:

m = Mass of car = $\dfrac{W}{g}$

W = Weight of car = 12000 N

a = Acceleration = 0.96 m/s²

Velocity of the car

$v=82\times \dfrac{1000}{3600}\\\Rightarrow v=\dfrac{82}{3.6}\\\Rightarrow v=\dfrac{41}{1.8}$

From the question

$F=300+1.8v^2\\\Rightarrow F=300+1.8\times \left(\dfrac{41}{1.8}\right)^2\\\Rightarrow F=1233.88\ N$

Balancing the forces

$\dfrac{P}{v}-1233.88=ma\\\Rightarrow P=(ma+12000)v\\\Rightarrow P=\left(\dfrac{12000}{9.81}\times 0.96+1233.88\right)\dfrac{41}{1.8}\\\Rightarrow P=54853.26055\ W=\dfrac{54853.26055}{746}\\\Rightarrow P=73.52983\ Hp$

The power is 73.52983 Hp

6 0

4 years ago

What is the net force on a race car with a mass of 1200 kg if its acceleration is 32.0m/s2 West?

frosja888 [35]

Answer:

38400N

Explanation:

F=mass×acceleration

=1200×32

=38400

3 0

3 years ago