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Yuri [45]
1 year ago
5

Estimate how long it would take one person to mow a football field using an ordinary home lawn mower. suppose that the mower mov

es with a 1-km/h speed, has a 0.5-m width, and a field is 360 ft long and 160 ft wide. 1 m = 3.281 ft.
Physics
1 answer:
HACTEHA [7]1 year ago
4 0
<span>10.7 hours Since we've been told that we have a speed of 1 km/h and a width of 0.5 meters that means that after 1 hour, we can mow a path 0.5 m wide and 1000 m long for a total area of 1000 m * 0.5 m = 500 m^2/hr. Now let's calculate the area of that football field. 360 ft / 3.281 ft/m * 160 ft / 3.281 ft/m = 5350.692864 m^2 Now let's divide that area by the 500 m^2 calculated earlier to see how many hours it will take. 5350.692864 m^2 / 500 m^2/hr = 10.70138573 hr So it would take about 10.7 hours to mow the football field.</span>
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A tennis player hits a ball 2.0 m above the ground. The ball leaves his racquet with a speed of 20 m/s at an angle 5.0 ∘ above t
ipn [44]

Answer:

ball clears the net

Explanation:

v_{o} = initial speed of launch of the ball = 20 ms^{-1}

\theta = angle of launch = 5 deg

Consider the motion of the ball along the horizontal direction

v_{ox} = initial velocity = v_{o} Cos\theta = 20 Cos5 = 19.92 ms^{-1}

t = time of travel

X = horizontal displacement of the ball to reach the net = 7 m

Since there is no acceleration along the horizontal direction, we have

X = v_{ox} t \\7 = v_{ox} t\\t = \frac{7}{v_{ox}}       Eq-1

Consider the motion of the ball along the vertical direction

v_{oy} = initial velocity = v_{o} Sin\theta = 20 Sin5 = 1.74 ms^{-1}

t = time of travel

Y_{o} = Initial position of the ball at the time of launch = 2 m

Y = Final position of the ball at time "t"

a_{y} = acceleration in down direction = - 9.8 ms⁻²

Along the vertical direction , position at any time is given as

Y = Y_{o} + v_{oy} t + (0.5) a_{y} t^{2}\\Y = 2 + (20 Sin5) (\frac{7}{20 Cos5}) + (0.5) (- 9.8) (\frac{7}{20 Cos5})^{2}\\Y = 2.00758 m\\

Since Y > 1 m

hence the ball clears the net

7 0
2 years ago
A box of mass 3kg is lifted 1.5m onto a shelf. Calculate the change in its gravitational potential energy. The gravitational fie
Vedmedyk [2.9K]

Answer:

The change in gravitational potential energy is 45 J.

Explanation:

Given that,

Mass = 3 kg

Distance = 1.5 m

Gravitational field strength = 10 N/kg

We need to calculate the change in gravitational potential energy

Using formula of  gravitational potential energy

Change\ in\ gravitational\ potential\ energy =gravitational\ field\ strength\times mass\times distance

Put the value into the formula

Change\ in\ gravitational\ potential\ energy =10\times3\times1.5

Change\ in\ gravitational\ potential\ energy =45\ J

Hence, The change in gravitational potential energy is 45 J.

5 0
2 years ago
A migrating salmon heads in the direction n 45° e, swimming at 2 mi/h relative to the water. the prevailing ocean currents flow
Sophie [7]
Calculate for the x and y-components of the velocities involved in this item.

 2 mi/h (45° east)
  x-component = (2 mi/h)(sin 45°)
                     = 1.41 mi/h
  y-component = (2 mil/h)(cos 45°)
                     = 1.41 mi/h

4 mi/h (east)
  x-component = 4 mi/h
  y-component = 0 mi/h

Adding up the corresponding components:
     x-component = 5.4142 mi/h

     y-component = 1.4142 mi/h

Calculating for the resultant,
        R = sqrt ((x²) + (y²))
   
        R = sqrt ((5.4142 mi/h)² + (1.4142 mi/h)²)
             R = 5.60 mi/h

Answer: 5.6 mi/h
5 0
2 years ago
When you urinate, you increase pressure in your bladder to produce the flow. For an elephant, gravity does the work. An elephant
weqwewe [10]

Answer:

a) v =  1.19 m / s , b)   P₁ = 0.922 10⁵ Pa

Explanation:

1) Let's use the fluid continuity equation

       Q = A v

The area of ​​a circle is

      A = π r2 = π d²/4

     

     v = Q / A = Q 4 / pi d²

     v = 0.006 4/π 0.08²

     v =  1.19 m / s

2) write Bernoulli's equation, where point 1 is the bladder and point 2 is the urine exit point

     P₁ + ½ rho v₁² + rho g y₁ = P₂ + ½ rho v₂² + rho g y₂

The exercise tell us

P₂ = 1.0013 105 Pa

v₁ = 0

y₁ = 1 m

y₂=0  

Rho (water) = 1000 kg / m³

      P₁ + rho y₁ = P₂ + ½ rho v₂²

      P₁ = P₂ + ½ rho v₂² - rho g y₁

      P₁ = 1.013 10⁵ + ½ 1000 (1.19)² - 1000 9.8 1

      P₁ = 1.013 10⁵ +708.5  - 9800

      P₁ =  92208.5Pa

      P₁ = 0.922 10⁵ Pa

8 0
1 year ago
Kate is researching air pollution and finds some information on ozone. She knows that ozone is a good thing as part of the ozone
jek_recluse [69]

"At ground level, ozone contributes to smog" so it is also an air pollutant.

Option: A

<u>Explanation</u>:

ozone is naturally present in stratosphere and acts as shield against harmful ultraviolet radiations. But it acts a pollutant contributing to global warming when it is present in lower level atmosphere particularly troposphere. In this level it combines with primary pollutants that is "nitrogen oxides" and "volatile organic" compounds to form secondary pollutant which absorbs outgoing radiation and contributes in raising the temperature. It has harmful impacts on vegetation as well as human health.

7 0
2 years ago
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