/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 50 A \(1000-\mathrm{kg}\) auto trav... [FREE SOLUTION] | 91Ó°ÊÓ

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A \(1000-\mathrm{kg}\) auto travels up a \(3.0\) percent grade at \(20 \mathrm{~m} / \mathrm{s}\). Find the cruising power required, neglecting friction.

Short Answer

Expert verified
The required cruising power is 5886 W (or 5.886 kW).

Step by step solution

01

Understanding the scenario

We need to calculate the power required for an auto to travel up an incline. A 3.0% grade means the road rises 3 meters for every 100 meters of horizontal distance. We are given the mass of the car \(m = 1000\, \mathrm{kg}\) and its velocity \(v = 20\, \mathrm{m/s}\).
02

Calculate the gravitational force along the plane

First, we need to determine the force of gravity doing work against the car's motion. This force is given by \(F = m \cdot g \cdot \sin(\theta)\), where \(g = 9.81 \, \mathrm{m/s^2}\) is the acceleration due to gravity and \(\theta\) is the angle of the incline. Since the grade is 3.0 percent, \(\sin(\theta) = 0.03\). Thus, \[ F = 1000 \times 9.81 \times 0.03 = 294.3 \, \mathrm{N}. \]
03

Calculate the power required

Power is the rate of doing work. For an object moving at constant speed up an incline, the required power \(P\) is given by \(P = F \cdot v\). Substituting the values we know, \[ P = 294.3 \, \mathrm{N} \times 20 \, \mathrm{m/s} = 5886 \, \mathrm{W} \] or approximately, \(5.886 \, \mathrm{kW}\).
04

Finalize and review the answer

The cruising power required for the car to move up the 3% grade at 20 m/s while neglecting friction is \(5886\, \mathrm{W}\). This is based solely on overcoming the component of the gravitational force. Review the calculations to ensure all unit conversions and arithmetic are correct.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Incline Problems
Incline problems in physics often involve understanding how objects move on a slope. An incline, or a sloped surface, is a common scenario in physics problems, especially when calculating forces. In this exercise, the incline is defined by a 3% grade, which means for every 100 meters of horizontal distance, the elevation changes by 3 meters.
When solving incline problems, it's essential to recognize the role gravity plays. Gravity acts downward, and on an incline, we need to consider its components along the plane of the incline. This allows us to compute the effective force that needs to be overcome to move the object up the slope.
Preliminary understanding of trigonometry might be required to determine angles or grades, but in this exercise, it's simplified by the percentage grade given. Ultimately, identifying this grade is key to solving the problem efficiently.
Power Calculation
Power is a crucial concept in physics, especially when discussing energy transfer over time. It measures how quickly work is done. In the context of moving an object up an incline, power represents the rate at which an external force must work to overcome the gravitational pull down the slope.
In the given problem, the power required is calculated using the formula: \\( P = F \times v \) \where \( F \) is the net force acting against the direction of movement and \( v \) is the constant velocity of the object moving up the incline.
Here it's noteworthy that power is measured in watts (W), and by converting smaller units, for easier comprehension, we deduce that the result is roughly 5.886 kilowatts (kW). This displays how the rate of energy expenditure increases with greater resistance, showing the importance of power calculations in practical applications such as automotive engineering.
Work and Energy
Work and energy are intertwined in physics as they both describe the transfer of energy from one system to another. Work is done when a force causes an object to move. The formula for work is \( W = F \times d \times \cos(\theta) \), where \( F \) is the force applied, \( d \) is the displacement, and \( \theta \) is the angle between the force and the direction of motion.
In this scenario, the car traveling up an incline doesn't show visible displacement through the work formula. Instead, it focuses on the power needed to continue its constant velocity despite opposing gravitational work.
Energy, in this context, is evident in the effort required to maintain the car’s motion. This energy is constantly transferred to overcome gravitational forces and keep the car moving upwards, reinforcing the significant role of kinetic energy during constant speed motion on an incline.
Forces on Inclines
Forces on an incline are a common challenge in classical mechanics. They determine the effort required to move objects along a sloped surface. Gravity, the primary force in incline problems, is split into two components: one perpendicular to the slope and one parallel to it.
This exercise simplifies the component calculations by using the given 3% grade. Here, with \( \sin(\theta) = 0.03 \), the effective gravitational component acting against the car’s motion along the incline is calculated.
Due to the way forces work, understanding how these calculations reflect reality is pivotal. The component of gravitational force, when multiplied by the velocity of the car, gives us the power required to sustain motion, highlighting the synergistic relationship between forces and incline angles.

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Most popular questions from this chapter

An engine expends \(40.0\) hp in propelling a car along a level track at a constant speed of \(15.0 \mathrm{~m} / \mathrm{s}\). How large is the total retarding force acting on the car? Remember that \(1 \mathrm{hp}=745.7 \mathrm{~W}\).

A \(0.50-\mathrm{kg}\) ball falls past a window that is \(1.50 \mathrm{~m}\) in vertical length. \((a)\) How much did the \(\mathrm{KE}\) of the ball increase as it fell past the window? ( \(b\) ) If its speed was \(3.0 \mathrm{~m} / \mathrm{s}\) at the top of the window, what was its speed at the bottom?

A force of \(1.50 \mathrm{~N}\) acts on a \(0.20-\mathrm{kg}\) cart so as to uniformly accelerate it along a straight air track. The track and force are horizontal and in line. How fast is the cart going after acceleration from rest through \(30 \mathrm{~cm}\), if friction is negligible? The work done by the force causes, and is equal to, the increase in \(\mathrm{KE}\) of the cart. Therefore, $$ \text { Work done }=(\mathrm{KE})_{\text {end }}-(\mathrm{KE})_{\text {start }} \quad \text { or } \quad F s \cos 0^{\circ}=\frac{1}{2} m v_{f}^{2}-\mathbf{0} $$ Substituting gives $$ (1.50 \mathrm{~N})(0.30 \mathrm{~m})=\frac{1}{2}(0.20 \mathrm{~kg}) v_{f}^{2} $$ from which \(v_{f}=2.1 \mathrm{~m} / \mathrm{s}\)

Figure \(6-3\) shows a bead sliding on a wire. If friction forces are negligible and the bead has a speed of \(200 \mathrm{~cm} / \mathrm{s}\) at \(A\), what will be its speed \((a)\) at point \(B ?\) (b) At point \(C\) ? The energy of the bead is conserved, so we can write Change in \(\mathrm{KE}+\) change in \(\mathrm{PE}_{\mathrm{G}}=0\) $$ \frac{1}{2} m v_{f}^{2}-\frac{1}{2} m v_{i}^{2}+m g\left(h_{f}-h_{i}\right)=0 $$ (a) Here, \(v_{i}=2.0 \mathrm{~m} / \mathrm{s}, h_{i}=0.80 \mathrm{~m}\), and \(h_{f}=0\). Using these values, while noticing that \(m\) cancels out, gives \(v_{f}=4.4 \mathrm{~m} / \mathrm{s}\) (b) Here, \(v_{b}=2.0 \mathrm{~m} / \mathrm{s}, h_{i}=0.80 \mathrm{~m}\), and \(h_{f}=0.50 \mathrm{~m} .\) Using these values leads to \(v_{f}=3.1 \mathrm{~m} / \mathrm{s}\). Alternative Method Since energy, \(\mathrm{E}\), is conserved, $$ \begin{aligned} \mathrm{E}_{i} &=\mathrm{E}_{f} \\ \mathrm{KE}_{i}+\mathrm{PE}_{\mathrm{G}} &=\mathrm{KE}_{f}+\mathrm{PE}_{\mathrm{G} f} \\ \frac{1}{2} m v_{i}^{2}+m g h_{i} &=\frac{1}{2} m v_{f}^{2}+m g h_{f} \\ \frac{1}{2} v_{1}^{2}+g h_{i} &=\frac{1}{2} v_{f}^{2}+g h_{f} \\ (2.00 \mathrm{~m} / \mathrm{s})^{2}+2\left(9.81 \mathrm{~m} / \mathrm{s}^{2}\right)\left(0.80 \mathrm{~m}-h_{f}\right)=v_{f}^{2} \end{aligned} $$

A proton \(\left(m=1.67 \times 10^{-27} \mathrm{~kg}\right)\) that has a speed of \(5.0 \times 10^{6} \mathrm{~m} / \mathrm{s}\) passes through a metal film of thickness \(0.010 \mathrm{~mm}\) and emerges with a speed of \(2.0 \times 10^{6} \mathrm{~m} / \mathrm{s}\). How large an average force opposed its motion through the film?

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