The post For a cycle, is the net work necessarily zero? For what kind of systems will this be the case? appeared first on the free answer.

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Answer:

For a cyclic process, the network is not necessarily being zero for all systems except for adiabatic systems.

For adiabatic systems, the heat transfer, *Q* is zero. From first law of thermodynamics the work interaction is equal to heat interactions in a system undergoing cyclic process.

For adiabatic systems, then,

So, for adiabatic systems undergoing cyclic process the net work is also zero.

The post For a cycle, is the net work necessarily zero? For what kind of systems will this be the case? appeared first on the free answer.

]]>The post A damaged 1200-kg car is being towed by a truck. Neglecting the friction, air drag, and rolling resistance, determine the extra power required (a) for constant velocity on a level road, (b) for constant velocity of 50 km/h on a 30° (from horizontal) uphill road, and (c) to accelerate on a level road from stop to 90 km/h in 12 s. appeared first on the free answer.

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Answer:

2760-2-41P SA Code: 2981

SR Code: 5070

Given data:

The mass of a the car,

The acceleration due to gravity,

(a) For constant velocity on level road:

The work needed to accelerate a body is simply the change in the kinetic energy of the car on a level road

Here at constant velocity the work done due to acceleration is zero.

Power required,

(b) On a uphill road with constant velocity

The slope of the uphill road

The work needed to accelerate a body is simply the change in the kinetic energy of the car and the change in the potential energy of the car.

Where, since at constant velocity acceleration is zero.

The power required is determined by work per unit time

We know that,

The velocity of the car, given

Power required,

(c) Acceleration on a level road

Due to no elevation of the road the potential energy will be zero

i.e.

The car accelerates from rest to

Therefore kinetic energy

Therefore the power required

Power required,

The post A damaged 1200-kg car is being towed by a truck. Neglecting the friction, air drag, and rolling resistance, determine the extra power required (a) for constant velocity on a level road, (b) for constant velocity of 50 km/h on a 30° (from horizontal) uphill road, and (c) to accelerate on a level road from stop to 90 km/h in 12 s. appeared first on the free answer.

]]>The post Determine the power required for a 1150-kg car to climb a 100-m-long uphill road with a slope of 30° (from horizontal) in 12 s (a) at a constant velocity, (b) from rest to a final velocity of 30 m/s, and (c) from 35 m/s to a final velocity of 5 m/s. Disregard friction, air drag, and rolling resistance. appeared first on the free answer.

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Answer:

Draw the diagram shows the slope of the uphill as shown below:

Use sine formula to calculate the value of *h*

Here, *h* is the vertical height of the uphill, *d* is the length of the uphill.

Substitute

Calculate the work done in climbing the uphill road will be stored in the form of potential energy in the car

Here, is the mass of the car, *g *is the acceleration due to gravity

Substitute and

Calculate the Power required for car

Substitute for time

Power required for the car to climb uphill is

b)

Initial velocity, 0

Final velocity, 30 m/s

On reaching 100 m uphill, the car has both potential and kinetic energy. This is due to the effect of work done on it.

Calculate the total work done

Substitute

Calculate the Power required

Therefore, Power required for the car to climb uphill is

(c)

Initial velocity,

Final velocity,

Calculate the total work done

The post Determine the power required for a 1150-kg car to climb a 100-m-long uphill road with a slope of 30° (from horizontal) in 12 s (a) at a constant velocity, (b) from rest to a final velocity of 30 m/s, and (c) from 35 m/s to a final velocity of 5 m/s. Disregard friction, air drag, and rolling resistance. appeared first on the free answer.

]]>The post A ski lift has a one-way length of 1 km and a vertical rise of 200 m. The chairs are spaced 20 m apart, and each chair can seat three people. The lift is operating at a steady speed of 10 km/h. Neglecting friction and air drag and assuming that the average mass of each loaded chair is 250 kg, determine the power required to operate this ski lift. Also estimate the power required to accelerate this ski lift in 5 s to its operating speed when it is first turned on. appeared first on the free answer.

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Answer:

Find the total mass of the ski lift by using the equation,

Here, *m* is average mass of each chair and *n* is number of chairs placed in 1 km length of ski lift.

Substitute 250 kg for *m* and for *n*.

Calculate the work needed to raise the ski lift through a vertical height (*h*) by using the equation,

Here, *g* is acceleration due to gravity and *h* is vertical rise of lift.

Substitute for *g* and 200 m for *h*.

Find the time at which the lift operates:

Here, *d* is distance travelled and *V* is average speed of the lift.

Substitute 1km for *d* and 10 km/h for *V*

Calculate the power required to operate the lift by using the equation,

Therefore, the power required to raise the lift is .

Calculate the acceleration of the lift in 5 sec.

Here, is change in velocity.

Calculate the work needed to accelerate a body is simply the change in the kinetic energy of the body by using the equation.

Calculate the power required to accelerate the ski lift in 5s by using the expression.

Therefore, power required during the acceleration is.

Calculate the vertical distance travelled during acceleration.

Calculate the power required due to gravity.

Calculate the total power required to operate the lift.

Therefore, the total power required to operate is.

The post A ski lift has a one-way length of 1 km and a vertical rise of 200 m. The chairs are spaced 20 m apart, and each chair can seat three people. The lift is operating at a steady speed of 10 km/h. Neglecting friction and air drag and assuming that the average mass of each loaded chair is 250 kg, determine the power required to operate this ski lift. Also estimate the power required to accelerate this ski lift in 5 s to its operating speed when it is first turned on. appeared first on the free answer.

]]>The post How much work, in kJ, can a spring whose spring constant is 3 kN/cm produce after it has been compressed 3 cm from its unloaded length? appeared first on the free answer.

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Answer:

2760-2-38P SA Code: 2981

SR Code: 5070

Given data:

Initial force,

Spring constant,

Initial length,

Final length,

The force at any point during the deflection of the spring is given by, where is the initial force and *x *is the deflection as measured from the point where the initial force occurred. The work required to compress the spring is

Therefore work required to compress the spring is

The work required to compress the spring,

The post How much work, in kJ, can a spring whose spring constant is 3 kN/cm produce after it has been compressed 3 cm from its unloaded length? appeared first on the free answer.

]]>The post A spring whose spring constant is 200 lbf/in has an initial force of 100 lbf acting on it. Determine the work, in Btu, required to compress it another 1 inch. appeared first on the free answer.

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Answer:

The force at any point during the deflection of the spring is given by,

where is the initial force

and *x *is the deflection as measured from the point where the initial force occurred.

The work required to compress the spring is

Therefore work required to compress the spring is

The work required to compress the spring in Btu is calculated by

Where 1Btu =778

The work required to compress the spring,

The post A spring whose spring constant is 200 lbf/in has an initial force of 100 lbf acting on it. Determine the work, in Btu, required to compress it another 1 inch. appeared first on the free answer.

]]>The post A 0.5-in diameter, 12-in-long steel rod with a Young’s modulus of 30,000 lbf/in2 is stretched 0.125 in. How much work does this require, in Btu? The strain work is given by where is the original volume of the solid, E is Young’s modulus and ε is the strain at the beginning and ending of the process. appeared first on the free answer.

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Answer:

Find the strain work by using the following equation:

…… (1)

Here, is the original volume of the solid, *E* is Young’s modulus, is the strain at the beginning of the process, and is the strain at the ending of the process,

Find the original volume of the rod by using the following equation:

Here, *D* is diameter of the rod and *L* is length of the rod.

Substitute 0.5 in for *D* and 12 in for .

Find the strain at the ending of the process by using the following equation:

Here, *dl* is change in length or stretched length.

Substitute 0.125 in. for *dl* and 12 in. for .

Substitute for , 0.010416 for , 0 for , and for *E* in equation (1).

Therefore, the work required during the process in Btu is .

The post A 0.5-in diameter, 12-in-long steel rod with a Young’s modulus of 30,000 lbf/in2 is stretched 0.125 in. How much work does this require, in Btu? The strain work is given by where is the original volume of the solid, E is Young’s modulus and ε is the strain at the beginning and ending of the process. appeared first on the free answer.

]]>The post A spherical soap bubble with a surface-tension of 0.005 lbf/ft is expanded from a diameter of 0.5 in to 2.0 in. How much work, in Btu, is required to expand this bubble? appeared first on the free answer.

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Answer:

Convert the units of from in. to ft.

Here, is the final diameter of the bubble.

Convert the units of from in. to ft.

Here, is the initial diameter of the bubble.

Express the work required to expand a soap bubble.

Here, work required to expand the soap bubble is *W*, surface tension of the soap bubble is , and area of the soap bubble is *A*.

Apply integration to find the work done.

Multiply by 2 since soap bubble has two interfaces.

Substitute for, for, for.

Therefore, the work required to expand the bubble is.

The post A spherical soap bubble with a surface-tension of 0.005 lbf/ft is expanded from a diameter of 0.5 in to 2.0 in. How much work, in Btu, is required to expand this bubble? appeared first on the free answer.

]]>The post The force F required to compress a spring a distance x is given by F- F0 = kx where k is the spring constant and F0 is the preload. Determine the work required to compress a spring whose spring constant is k= 200 lbf/in a distance of one inch starting from its free length where F0 = 0 lbf. Express your answer in both lbf-ft and Btu. appeared first on the free answer.

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Answer:

2760-2-34P SA Code: 2981

SR Code: 5070

Given data:

Preload,

Spring constant,

Initial length,

Final length,

The force at any point during the deflection of the spring is given by,

where is the initial force

and *x *is the deflection as measured from the point where the initial force occurred.

The work required to compress the spring is

Therefore work required to compress the spring is

The work required to compress the spring in is

The work required to compress the spring in Btu is calculated by

Where 1Btu =778

The work required to compress the spring in Btu is

The post The force F required to compress a spring a distance x is given by F- F0 = kx where k is the spring constant and F0 is the preload. Determine the work required to compress a spring whose spring constant is k= 200 lbf/in a distance of one inch starting from its free length where F0 = 0 lbf. Express your answer in both lbf-ft and Btu. appeared first on the free answer.

]]>The post A man weighing 180 lbf is pushing a cart that weights 100 lbf with its contents up a ramp that is inclined at an angle of 10° from the horizontal. Determine the work needed to move along this ramp a distance of 100 ft considering (a) the man and (b) the cart and its contents as the system. Express your answers in both lbf-ft and Btu. appeared first on the free answer.

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Answer:

Draw the free body diagram of the weight of the man and weight of the cart.

Write the weight component of cart along the ramp.

Write weight component of man along the ramp.

(a)

Consider man and its contents as the system and find the work done by the man on cart.

Here, *d* is the distance moved along the ramp.

Substitute 100 ft for *d*, for , and for

Therefore, work needed to move along the ramp when the man and its contents are considered as the system is or .

(b)

Consider cart and its contents as the system and find the work needed to move along the ramp.

Substitute 100 ft for *d* and for

Therefore, work needed to move along the ramp when the cart and its contents as the system is or .

The post A man weighing 180 lbf is pushing a cart that weights 100 lbf with its contents up a ramp that is inclined at an angle of 10° from the horizontal. Determine the work needed to move along this ramp a distance of 100 ft considering (a) the man and (b) the cart and its contents as the system. Express your answers in both lbf-ft and Btu. appeared first on the free answer.

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