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Art [367]
3 years ago
11

I'm giving out a lot of points for whoever helps me and answers correctly! 3 questions to answer! Please answer them ALL!!! :D

Physics
2 answers:
lions [1.4K]3 years ago
5 0

1-a 2-b 3-b    

srry had to write more, i go to this school














                                                                                                                 

Lemur [1.5K]3 years ago
3 0

1. A) A ball sits motionless on the ground

Newton's First Law of inertia states that:

"When the forces acting on an object are balanced, the object stays at rest (if it was at rest) or continues its motion with constant velocity (if it was in motion)"

Among the options given, we see that the option

A) A ball sits motionless on the ground

is an example of this law: in fact, the ball sits at rest on the ground, the forces acting on it are balanced, so the ball stays at rest.

2. B) The earth pulls more on the shuttle

The gravitational attraction exerted by a planet on the shuttle is given by

F=G\frac{Mm}{r^2}

where

G is the gravitational constant

M is the mass of the planet

m is the mass of the shuttle

r is the distance between the shuttle and the planet

In this problem, we are comparing the gravitational pulls exerted by the Earth and the Moon on the shuttle. The distance, r, is the same (because the shuttle is half-way), the mass of the shuttle m is the same, and G is the same. However, the mass of the Earth is greater than the mass of the Moon, so in the formula M is greater for the Earth: therefore, the Earth pulls more on the shuttle.

3. B) The velocity of the car reduced from 50 km/h to 35 km/h over one minute

The acceleration of the car is defined as the ratio between the change in velocity and the time taken:

a=\frac{v_f-v_i}{\Delta t}

where vf is the final velocity, vi is the initial velocity, and \Delta t is the time taken.

In order to have a negative acceleration, the numerator must be negative: this means that the initial velocity, vi, must be greater than the final velocity, vf, and this situation occurs in option B), since the initial velocity is 50 km/h while the final velocity is 35 km/h.

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What is the best definition of vectors?
mariarad [96]

Answer:

Number value and direction

Explanation:

Vectors are quantities that can be identified by value and direction . Examples are velocity and acceleration

8 0
3 years ago
A steam Rankine cycle operates between the pressure limits of 1500 psia in the boiler and 2 psia in the condenser. The turbine i
AlladinOne [14]

Answer:

a. Mass flow rate through the boiler = 5.462lbm/s

b. Power produced by the turbine = 2525.8kW

c. The rate of heat supply in the boiler = 6901.42Btu/s

d. Thermal efficiency of the cycle = 34.3%

Explanation:

In order to provide a solution, we must assume that ;

- The system is operating at a steady condition

- Kinetic and potential energy changes are negligible

Now from steam tables, we calculate specific volume v and enthalpy h as,

h_1 = 95.96Btu/lb (  h_1 = h_f at 2psia )

v_1 = 0.016238ft^3/lb ( v_1 = v_f at 2psia )

w_{p,in} = v_1(P_2-P_1) = 0.016238(1500-2) * \frac{1}{5.404} = 4.501 Btu/lb

w_p = h_2 - h_1\\h_2 = w_p+h_1=4.501+95.96=100.461Btu/lb

h_3 = 1364.0Btu/lb

s_3 = 1.5073Btu/lb.R

( at P_3 = 1500psia & T_3 = 800^0F )

P_4 = 2psia\\S_4 = S_3\\x_4S = \frac{S_4-S_f}{S_{fg}}=\frac{1.5073-0.1783}{1.7374}=0.765

( S_f & S_{fg} when pressure is 2psia)

h_4S = h_f+x_4S*h_{fg}=95.96+(0.765)(1021.0)=877.025Btu/lb

n_T= \frac{h_3-h_4}{h_3-h_4S}\\ h_4=h_3-n_T(h_3-h_4S)=1364.0-0.90(1364.0-877.025)=925.7Btu/lb

Therefore,

q_{in}=h_3-h_2=1364.0-100.461=1263.54Btu/lb\\q_{out}=h_4-h_1=925.7-95.96=829.74Btu/lb\\w_{net}=q_{in}-q_{out}=1263.54-829.74=433.8Btu/lb

To calculate the mass flow rate of steam in the cycle, we use the formula

W_{net}=mw_{net}\\m=\frac{W_{net}}{w_{net}} =\frac{2500}{433.8}=5.763*(\frac{0.94782Btu}{1Kj} )=5.462lb/s

where 1Kj = 0.947817 Btu

The power output and the rate of heat addition are calculated thus,

W_{T,out}=m(h_3-h_4)=(5.462lb/s)*(1364-925.7)Btu/lb*(\frac{1Kj}{0.94782Btu} )\\=5.462*438.3*1.055=2525.8KW

Q_{in}=mq_{in}=5.462(1263.54)=6901.46Btu/s

The thermal efficiency of the cycle can be found thus;

n_{th}=\frac{W_{net}}{Q_{in}} =\frac{2500}{6901.46}*(\frac{0.94782Btu}{1Kj} ) =0.343

= 34.3%

5 0
3 years ago
The half-life of plutonium 239 is 24,200 years. Assume that the decay rate is proportional to the amount. Determine the amount o
kotykmax [81]

Answer:

time taken is equal to 14,156 years

Explanation:

we know,

Y=Ae^{-kt}

at t = 0

Y(0) = A

given that half life of plutonium 239 = 24,200

\dfrac{A}{2}=Ae^{-kt}\\0.5=e^{-kt}\\k\times 24200 = ln(2)\\k = \dfrac{ ln(2)}{24200}

Y=Ae^{-kt}

\frac{3}{2} = e^{-kt}\\ln(1.5)=-\dfrac{ ln(2)}{24200}\times t\\t=-\dfrac{ln(1.5)\times 24200}{ ln(2)}\\t=14,156 \ years

hence time taken is equal to 14,156 years

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3 years ago
Which of the following statements is true about magnetic fields produced by current-carrying wires?
VARVARA [1.3K]
I believe the answer is c. the longer the wire, the larger the magnetic field
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Explain How can you<br> use a distance-time graph<br> to calculate average<br> speed?
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Explanation:

Average speed = change in distance / change in time

In other words, the average speed is the slope of the line connecting two points on the graph.

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