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3 years ago

The force of gravity acting on a child's mass on earth is 490 newtons. what's the child's mass?

Physics

2 answers:

UNO [17]3 years ago

6 0

F = m • a

What we know:
- Gravity: 9.8 m/s
- Force: 490 N

Equation derived:
m = F/a
m = 490/9.8
= 50 kg

disa [49]3 years ago

6 0

50 kg because e = mc2

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Steam is to be condensed on the shell side of a heat exchanger at 150 oF. Cooling water enters the tubes at 60 oF at a rate of 4

zalisa [80]

Answer:

a. 572Btu/s

b.0.1483Btu/s.R

Explanation:

a.Assume a steady state operation, KE and PE are both neglected and fluids properties are constant.

From table A-3E, the specific heat of water is $c_p=1.0\ Btu/lbm.F$ , and the steam properties as, A-4E:

$h_{fg}=1007.8Btu/lbm, s_{fg}=1.6529Btu/lbm.R$

Using the energy balance for the system:

$\dot E_{in}-\dot E_{out}=\bigtriangleup \dot E_{sys}=0\\\\\dot E_{in}=\dot E_{out}\\\\\dot Q_{in}+\dot m_{cw}h_1=\dot m_{cw}h_2\\\\\dot Q_{in}=\dot m_{cw}c_p(T_{out}-T_{in})\\\\\dot Q_{in}=44\times 1.0\times (73-60)=572\ Btu/s$

Hence, the rate of heat transfer in the heat exchanger is 572Btu/s

b. Heat gained by the water is equal to the heat lost by the condensing steam.

-The rate of steam condensation is expressed as:

$\dot m_{steam}=\frac{\dot Q}{h_{fg}}\\\\\dot m_{steam}=\frac{572}{1007.8}=0.5676lbm/s$

Entropy generation in the heat exchanger could be defined using the entropy balance on the system:

$\dot S_{in}-\dot S_{out}+\dot S_{gen}=\bigtriangleup \dot S_{sys}\\\\\dot m_1s_1+\dot m_3s_3-\dot m_2s_2-\dot m_4s_4+\dot S_{gen}=0\\\\\dot m_ws_1+\dot m_ss_3-\dot m_ws_2-\dot m_ss_4+\dot S_{gen}=0\\\\\dot S_{gen}=\dot m_w(s_2-s_1)+\dot m_s(s_4-s_3)\\\\\dot S_{gen}=\dot m c_p \ In(\frac{T_2}{T_1})-\dot m_ss_{fg}\\\\\\\dot S_{gen}=4.4\times 1.0\times \ In( {73+460)/(60+460)}-0.5676\times 1.6529\\\\=0.1483\ Btu/s.R$

Hence,the rate of entropy generation in the heat exchanger. is 0.1483Btu/s.R

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3 years ago

A roller coaster's velocity at the top of the hill is 10 m/s. Two seconds later it reaches the bottom of the hill with a velocit

svet-max [94.6K]

your answer is 8 m / sec²

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2 years ago

Which conditions are low air pressure systems usually associated with?

Inga [223]

cloudy, wet weather

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A car traveling north with a velocity of 33 m/sec slows down to a velocity of 12 m/sec north within 10 sec. What is the car’s de

strojnjashka [21]

a=v/t

v= 33-12 = 21

21÷10=2.1

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2 years ago

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a catcher "gives" with the ball when he catches a 0.196 kg baseball moving at 31 m/s. if he moves his glove a distance of 5.32 c

Aloiza [94]

Answer:

3540.5N

Explanation:

Step one:

given data

mass m= 0.196kg

speed v= 31m/s

distance r= 5.32cm = 0.0532m

Step two

The expression relating force, mass, velocity and distance is

F= mv^2/r

substitute we have

F=0.196*31^2/0.0532

F=0.196*961/0.0532

F=188.356/0.0532

F=3540.5N

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2 years ago