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Vlad [161]
3 years ago
9

A car travels 40 kilometers at an average speed of 80km/h and then travels 40 kilometers at an average speed of 40km/h. The aver

age speed of the car for this 80-km trip is
Physics
1 answer:
iris [78.8K]3 years ago
8 0

Speed = distance / time

Part 1: 40 km at 80 km per goir = 0.50 hours

Part 2: 40 km at 40 km per hour = 1 hour

The time of the trip was 1.5 hours

Total distance was 40 + 40 = 80 ins.

Speed = distance / time = 80/1.5 = 53.33 km/he ( round answer as needed)

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If an object is projected horizontally from a height of 5 m with an initial velocity of 7 m/s, what is the value of x0?
tatiyna
ANSWER IS D X0=9.8m/s^2
5 0
2 years ago
Water enters the constant 130-mm inside-diameter tubes of a boiler at 7 MPa and 65°C and leaves the tubes at 6 MPa and 450°C wit
snow_lady [41]

The inlet velocity is 1.4 m/s and inlet volume is 0.019 m³/s.

Explanation:

When water entering the tube of constant diameter flows through the tube, it exhibits continuity of mass in the hydrostatics. So the mass of water moving from the inlet to the outlet tend to be same, but the velocity may differ.

As per mass flow equality which states that the rate of flow of mass in the inlet is equal to the product of area of the tube with the velocity of the water and the density of the tube.

Since, the inlet volume flow is measured as the product of velocity with the area.

Inlet volume flow=Inlet velocity*Area*time

And the mass flow rate is  

Mass flow rate in the inlet=density*area*inlet velocity*time

Mass flow rate in the outlet=density*area*outlet velocity*time

Since, the time and area is constant, the inlet and outlet will be same as

(Mass inlet)/(density*inlet velocity)=Area*Time

(Mass outlet)/(density*outlet velocity)=Area*Time

As the ratio of mass to density is termed as specific volume, then  

(Specific volume inlet)/(Inlet velocity)=(Specific volume outlet)/(Outlet velocity)

Inlet velocity=  (Specific volume inlet)/(Specific volume outlet)*Outlet velocity

As, the specific volume of water at inlet is 0.001017 m³/kg and at outlet is 0.05217 m³/kg and the outlet velocity is given as 72 m/s, the inlet velocity

is

Inlet velocity = \frac{0.001017}{0.05217}*72 =1.4035 m/s

So, the inlet velocity is 1.4035 m/s.

Then the inlet volume will be

Inlet volume = inlet velocity*area of circle=\pi  r^{2}*inlet velocity

As the diameter of tube is 130 mm, then the radius is 65 mm and inlet velocity is 1.4 m/s

Inlet volume = 1.4*3.14*65*65*10^{-6} =0.019 \frac{m^{3} }{s}

So, the inlet volume is 0.019 m³/s.

Thus, the inlet velocity is 1.4 m/s and inlet volume is 0.019 m³/s.

4 0
3 years ago
How long can you keep string cheese in the fridge?
allsm [11]
Cheese attributes its sour taste because of its lactic acid content. However, this should not be an indication to whether the cheese is spoiling already. We can tell its expiry date through the manufacturing details of the product. The product should be good to consume before the manufacturing expiry date. Every package must include expiry date in order to inform the consumer about the range of its consumability attributes. In the case where molds are present on the cheese already, cheese on some parts may not be edible already. Molds are due to the oxidation of glucose through the action of specific bacteria.
8 0
4 years ago
Alex, parked by the side of an east-west road, is watching car P, which is moving in a westerly direction. Barbara, driving east
Alexxandr [17]

Answer:

v_{PB} = 130\ km/h

Explanation:

Since, Alex is at rest. Therefore, the speed measured by him will be the absolute speed of car P. Therefore, taking easterly direction as positive:

Absolute\ Velocity\ of\ Car\ P = v_{P} = -78\ km/h

And the absolute velocity of Barbara's Car is given as:Absolute\ Velocity\ of\ Barbara's\ Car = v_{B} = 52\ km/h

Now, for the velocity of Car p with respect to the velocity of Barbara's Car can be given s follows:

Velocity\ of\ Car\ P\ measured\ by\ Barbara = v_{PB} = v_{B}-v_{P}\\\\v_{PB} = 52\ km/h-(-78\ km/h)

v_{PB} = 130\ km/h

6 0
3 years ago
2. At noon, ship A was 12 nautical miles due north of ship B. Ship A was sailing south at 12 knots (nautical miles per hour; a n
AleksandrR [38]

Answer:

No

Explanation:

Let the reference origin be location of ship B in the beginning. We can then create the equation of motion for ship A and ship B in term of time t (hour):

A = 12 - 12t

B = 9t

Since the 2 ship motions are perpendicular with each other, we can calculate the distance between 2 ships in term of t

d = \sqrt{A^2 + B^2} = \sqrt{(12 - 12t)^2 + (9t)^2}

For the ships to sight each other, distance must be 5 or smaller

d \leq 5

\sqrt{(12 - 12t)^2 + (9t)^2} \leq 5

(12 - 12t)^2 + (9t)^2 \leq 25

144t^2 - 288t + 144 + 81t^2 - 25 \leq 0

225t^2 - 288t + 119 \leq 0

(15t)^2 - (2*15*9.6)t + 9.6^2 + 26.84 \leq 0

(15t^2 - 9.6)^2 + 26.84 \leq 0

Since (15t^2 - 9.6)^2 \geq 0 then

(15t^2 - 9.6)^2 + 26.84 > 0

So our equation has no solution, the answer is no, the 2 ships never sight each other.

8 0
4 years ago
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