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alekssr [168]
3 years ago
10

A power lifter performs a dead lift, raising a barbell with a mass of 305 kg to a height of 0.42 m above the ground, giving the

barbell 1256.66 J of potential energy. The power lifter then releases the barbell, letting it drop towards the ground. Determine the magnitude of the vertical velocity of the barbell when it reaches a height of 0.21 m (on the way down) using a mechanical energy approach. Then calculate the velocity right as it reaches the ground using a mechanical energy approach. Confirm your answer for the velocity of the barbell right before it hits the ground by also calculating this velocity using a projectile motion approach.
Physics
1 answer:
Ann [662]3 years ago
3 0

Answer:

Explanation:

Before it hits the ground:

The initial potential energy = the final potential energy + the kinetic energy

mgH = mgh + 1/2 mv²

gH = gh + 1/2 v²

v = √(2g (H - h))

v = √(2 * 9.81 m/s² * (0.42 m - 0.21 m))

v ≈ 2.0 m/s

When it hits the ground:

Initial potential energy = final kinetic energy

mgH = 1/2 mv²

v = √(2gH)

v = √(2 * 9.81 m/s² * 0.42 m)

v ≈ 2.9 m/s

Using a kinematic equation to check our answer:

v² = v₀² + 2a(x - x₀)

v² = (0 m/s)² + 2(9.8 m/s²)(0.42 m)

v ≈ 2.9 m/s

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A jogger hears a car alarm and decides to investigate. While running toward the car, she hears an alarm frequency of 872.10 Hz.
Nata [24]

Answer:

v = 4.18 m/s

Explanation:

given,

frequency of the alarm = 872.10 Hz

after passing car frequency she hear = 851.10 Hz

Speed of sound = 343 m/s

speed of the jogger = ?

speed of the

v_f = \dfrac{872.10-851.10}{2}

v_f =10.5\ Hz

v_o = 872.1 - 10.5

V_0 = 861.6\ Hz

The speed of jogger

v = \dfrac{v_1 \times 343}{v_0}-343

v = \dfrac{872.1 \times 343}{861.6}-343

v = 4.18 m/s

5 0
2 years ago
If the person drops box from 3.8 m how much energy is transferred from potential energy to kinetic energy
kotykmax [81]

Answer:

Kinetic energy

When work is done the energy is transferred from one type to another. This transferred energy may appear as kinetic energy.

For example, when you pedal your bicycle so that its speed increases, you are doing work to transfer chemical energy from your muscles to the kinetic energy of the bicycle.

Kinetic energy is the energy an object possesses by virtue of its movement. The amount of kinetic energy possessed by a moving object depends on the mass of the object and its speed. The greater the mass and the speed of the object the greater its kinetic energy.

The kinetic energy Ek of an object of mass m at a speed v is given by the relationship

{E_k} = \frac{1}{2}m{v^2}

m is the mass of the object in kilograms ( kg) and v is the speed of the object in metres per second ( m\,s^{-1}).

Explanation:

When work is done on an object it may also lead to energy being transferred to the object in the form of gravitational potential energy of the object.

Gravitational potential energy is the energy an object has by virtue of its position above the surface of the Earth. When an object is lifted, work is done. When work is done in raising the height of an object, energy is transferred as a gain in the gravitational potential energy of the object.

For example, suppose you lift a suitcase of mass m through a height h. The weight W of the suit case is a downward force of size mg. In lifting the suitcase, you would have to pull upwards on it with a force equal in size to its weight, mg.

Two suitcases. One has a green force arrow pointing up labelled F and a purple force arrow pointing down labelled 'Weight = mg'. The other case is raised by a height labelled h.

Suitcases with forces and height labelled

When this force (equal to the weight mg, but upwards) is applied to the suitcase over the distance h:

Work\,done=force\,\times\,distance\,upwards=mg\,\times\,h

This energy is transferred to potential energy when raising the object through a known height.

Energy = mass \times gravitational\,field\,strength \times height

E = m \times g \times h

This is the relationship used to calculate gravitational potential energy.

{E_p} = mgh

where m is the mass of the object in kilograms (kg), g is the gravitational field strength, (for positions near the surface of the Earth g = 9∙8 newtons per kilogram ( N kg ^{-1} and h is the height above the surface of the Earth in metres ( m).

8 0
3 years ago
How has the farming industry been affected by the use of fossil fuels?
Mashutka [201]

Fossil fuels have led to an increase in food costs.

Explanation:

Buried organic material over million of years form combustible geologic deposits of organic materials called fossil fuels that can be converted crude oil, natural gas, or coal.

Fossil fuel are currently used as a source of energy in machine and equipment applied in the farming industry. Mechanization has been made possible due to this type of fuel availability thus larger farms have been prepared for cultivation.In addition, other processes such as planting,weeding and harvesting are currently performed by farming machines which are propelled by fossil energy. So in general, fossil fuels in the farming industry has led to increase in amount of crop harvested because more farms are under cultivation and farming process is now mechanized. However, due to use of machines and energy, the production cost has increased, thus to cover for this increased cost, the prices for food products increases, making the cost of food commodities to rise.

Learn More

Fossil fuels: brainly.com/question/13660400

Keyword: Farming, industry, fossil fuel

#LearnwithBrainly

3 0
2 years ago
A piece of wood that floats on water has a mass of 0.0175 kg. A lead weight is tied to the wood, and the apparent mass with the
crimeas [40]

Answer:

Specific gravity is 0.56

Explanation:

We know that

mass of water displaced by the wood is, m1( apparent mass when wood in air and lead is submerged in water) - m2(the apparent mass when wood and lead both are submerged in water)

= 0.0765 - 0.0452 = 0.0313 Kg

So the specific gravity of the wood is, = mass of wood / mass of water displaced by the wood

= 0.0175/0.0313

=0.56

5 0
3 years ago
A physics professor did daredevil stunts in his spare time. His last stunt was an attempt to jump across a river on a motorcycle
tatiyna

Answer:

a) 17.8 m/s

b) 28.3 m

Explanation:

Given:

angle A = 53.0°

sinA = 0.8

cosA = 0.6

width of the river,d = 40.0 m,

the far bank was 15.0 m lower than the top of the ramp h = 15.0 m,

The river itself was 100 m below the ramp H = 100 m,

(a) find speed v

vertical displacement

-h= vsinA\times t-gt^2/2

putting values h=15 m, v=0.8

-15 = 0.8vt - 4.9t^2  ............. (1)

horizontal displacement d = vcosA×t = 0.6×v ×t

so v×t = d/0.6 = 40/0.6

plug it into (1) and get

-15 = 0.8\times40/0.6 - 4.9t^2

solving for t we get

t = 3.734 s

also, v = (40/0.6)/t = 40/(0.6×3.734) =  17.8 m/s

(b) If his speed was only half the value found in (a), where did he land?

v = 17.8/2 = 8.9 m/s

vertical displacement = -H =v sinA t - gt^2/2

⇒ 4.9t^2 - 8.9\times0.8t - 100 = 0

t = 5.30 s

then

d =v×cosA×t = 8.9×0.6×5.30= 28.3 m

3 0
2 years ago
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