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4 years ago

1 give reason

Physics

1 answer:

Anastaziya [24]4 years ago

4 0

Answer:

A. The melting of ice is both a desirable and undesirable change because, ice is needed to melt so as to make liquid water available for animal and plant use and consumption and also to release the energy used in the fusion process of ice formation. Melting of ice is undesirable because melting ice liberate water slowly, and the water liberated can erode surface soil. Melting ice reduces the available heat sink on earth and also reduces the available stored up fresh water supply on earth.

B. The appearance of hailey comet once every 72 year is a periodic change because it's motion around the solar system is repeated with time. The reason for this highly elliptical and eccentric path of motion is largely due to the gravitational effect of the sun and the planets on the comet.

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Una moto accelera da ferma a 80 km/h in 4,0 s. A quale forza di inerzia è sottoposto il pilota che ha massa 75 kg?

scoray [572]

A=65 divideded by 55 plus 1000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000

Explanation:

4 0

3 years ago

A motorbike travels 45 miles in 15 minutes, what is its speed (hint change the minutes to hours!!)

Flauer [41]

Answer:

180 miles/hr

Explanation:

15 min=1/4 hr

s= distance/time

s=45miles/1/4 hr

s=45miles x 4/1=180 miles/hr

6 0

3 years ago

A train travels at 270 km in 3 hours . what is the speed of the train?

Ann [662]

$270 \div 3 = 90km / h$

3 0

3 years ago

Read 2 more answers

A 75 kg football player is gliding forward across very smooth ice at 4.6 m/s. He throws a 0.47 kg football straight forward. A)

lord [1]

Answer:

4.53482 m/s

4.506 m/s

Explanation:

$m_1$ = Mass of player = 75 kg

$v_1$ = Initial velocity of player = 4.6 m/s

$m_2$ = Mass of ball = 0.47 kg

$v_1$ = Initial velocity of ball = 15 m/s

The linear momentum of the system is conserved

$(m_1+m_2)v_1=m_1v+m_2v_2\\\Rightarrow v=\dfrac{(m_1+m_2)v_1-m_2v_2}{m_1}\\\Rightarrow v=\dfrac{(75+0.47)4.6-0.47\times 15}{75}\\\Rightarrow v=4.53482\ m/s$

The player's speed is 4.53482 m/s

In the second case the equation of momentum is

$(m_1+m_2)v_1=m_1v+m_2(v_2+v_1)\\\Rightarrow v=\dfrac{(m_1+m_2)v_1-m_2(v_2+v_1)}{m_1}\\\Rightarrow v=\dfrac{(75+0.47)4.6-0.47\times (15+4.6)}{75}\\\Rightarrow v=4.506\ m/s$

The player's speed is 4.506 m/s

4 0

4 years ago

A piston–cylinder device with a set of stops initially contains 0.6 kg of steam at 1.0 MPa and 400°C. The location of the stops

Ilya [14]

Answer:

(a) Compression work at the final state with a pressure of 1(MPa) is: 44.32(KJ), (b) Compression work at the final state with a pressure of 500(KPa): 110.37(KJ) and (c) temperaure of the final state in part b: T=151.83(°C).

Explanation:

Remember that the substance is steam so it's water (H2O) and the initial conditions are $P_{1} =1MPa, T_{1}=400^{0}C, m=0.6Kg$ and $v_{2} =0.4v_{1}$ from a saturated water table and the initial conditions we can determine that the state phase is superheated (see Table 1 attached) because the $T_{sat}=179.88^{0} C \leq T_{1}$ from the table 1 we get: $v_{1} =0.30661(m^{3}/Kg)$ . Now we have second conditions as: $P_{2}=1(MPa), T_{2}=250^{0}C$ so from the same table we can see the state still superheated and we get $v_{2}=0.23275(m^{3}/Kg)$ , knowing that it's a isobaric process we can find the compression's work as: $W_{b}=m*P(v_{2}-v_{1})=0.6*1000*(0.23275-0.30661)=-44.32(KJ)$ so the compressor's work is: 44.32(KJ). (b) Then the piston reaches the stop and there are two processes in this stage, so Process 1 is isobaric and: $W_{1}=m*P*(v_{2}-v_{1}) =0.6*1000*(0.4*0.30661-0.30661)=-110.38(KJ)$ and the second process is isochoric: $W_{2}=zero$ ,now $W_{b}=W_{1}+ W_{2} =110.38+0=110.38(KJ)$ . Finally to get the temperarure at the final state in part (b) we get: $v_{2} =0.4v_{1} =0.4*0.30661=0.122644(m^{3}/Kg), P_{2}=500(KPa)$ from table 2 (see attached) we compare $v_{f}$ and $v_{g}$ at the saturated water table and find the following: $v_{f}=0.001093(m^{3}/Kg)$ , so we know that the final state phase is a satured mixture and we get the temperature at the final state as: $T_{2} =T_{sat} =151.83^{0}C$ .

3 0

4 years ago