/*! 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 13 The only force acting on a \(5.0... [FREE SOLUTION] | 91Ó°ÊÓ

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The only force acting on a \(5.0\) -kg object has components \(F_{x}=20 \mathrm{~N}\) and \(F_{y}=30 \mathrm{~N}\). Find the acceleration of the object. Use \(\sum F_{x}=m a_{x}\) and \(\sum F_{y}=m a_{y}\) to obtain $$ \begin{array}{l} a_{x}=\frac{\sum F_{x}}{m}=\frac{20 \mathrm{~N}}{5.0 \mathrm{~kg}}=4.0 \mathrm{~m} / \mathrm{s}^{2} \\ a_{y}=\frac{\sum F_{y}}{m}=\frac{30 \mathrm{~N}}{5.0 \mathrm{~kg}}=6.0 \mathrm{~m} / \mathrm{s}^{2} \end{array} $$ These components of the acceleration are shown in Fig. \(3-10 .\) From the figure, $$ a=\sqrt{(4.0)^{2}+(6.0)^{2}} \mathrm{~m} / \mathrm{s}^{2}=7.2 \mathrm{~m} / \mathrm{s}^{2} $$ and \(\theta=\arctan (6.0 / 4.0)=56^{\circ}\).

Short Answer

Expert verified
The acceleration is 7.2 m/s² at 56°.

Step by step solution

01

Calculate Acceleration in X-Direction

The force component in the x-direction is given as \( F_x = 20 \text{ N} \). Using Newton's second law, the acceleration \( a_x \) in the x-direction is calculated as follows: \[ a_x = \frac{F_x}{m} = \frac{20 \text{ N}}{5.0 \text{ kg}} = 4.0 \text{ m/s}^2 \].
02

Calculate Acceleration in Y-Direction

The force component in the y-direction is given as \( F_y = 30 \text{ N} \). Using Newton's second law, the acceleration \( a_y \) in the y-direction is calculated as follows: \[ a_y = \frac{F_y}{m} = \frac{30 \text{ N}}{5.0 \text{ kg}} = 6.0 \text{ m/s}^2 \].
03

Determine Resultant Acceleration Magnitude

The magnitudes of the accelerations in the x and y directions allow us to find the resultant acceleration using Pythagorean theorem: \[ a = \sqrt{(a_x)^2 + (a_y)^2} = \sqrt{(4.0 \text{ m/s}^2)^2 + (6.0 \text{ m/s}^2)^2} = 7.2 \text{ m/s}^2 \].
04

Find Direction of Resultant Acceleration

Given the accelerations \( a_x = 4.0 \text{ m/s}^2 \) and \( a_y = 6.0 \text{ m/s}^2 \), the direction \( \theta \) of the resultant acceleration can be determined by: \[ \theta = \arctan\left( \frac{a_y}{a_x} \right) = \arctan\left( \frac{6.0}{4.0} \right) = 56^\circ \].

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Key Concepts

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

Force Components
When dealing with forces, it's crucial to understand that they can be broken down into components. In this problem, we have two forces acting at right angles to each other: one in the x-direction and one in the y-direction. These are known as force components.
The force component in the x-direction is given as 20 N, and in the y-direction, it is 30 N. By breaking down the force into components, we can more easily analyze the motion and calculate quantities like acceleration in each direction.
For each component, the force influences the object independently along its direction. This breakdown adheres to Newton's Second Law, which lets us calculate acceleration separately for the x and y axes.
Resultant Acceleration
Resultant acceleration is the overall acceleration resulting from combining the individual accelerations in the x and y directions. When multiple forces are involved, they often don't act along the same line. Instead, they may act at angles to one another and thus need to be combined to find the resultant effect.
In our example, using the accelerations in the x and y directions computed from the force components, we must find out how quickly the object is speeding up in the combination of both directions. To find this overall or resultant acceleration, we employ the Pythagorean theorem as the accelerations are perpendicular.
Thus, our formula becomes \[ a = \sqrt{a_x^2 + a_y^2} \] where \(a_x = 4.0 \text{ m/s}^2\) and \(a_y = 6.0 \text{ m/s}^2\). This calculus provides a magnitude of \(a = 7.2 \text{ m/s}^2\), illustrating how combined forces influence acceleration.
Vector Magnitude
The idea of vector magnitude comes into play when we talk about the size or length of a vector in the context of acceleration. Since acceleration is a vector quantity, it has both direction and magnitude.
In this exercise, we calculate the vector magnitude of the resulting acceleration to quantify its strength without focusing on its direction.
The formula we've used, \(a = \sqrt{a_x^2 + a_y^2}\), determines how 'strong' the resultant acceleration vector is. This magnitude tells us just how fast the object is accelerating as a result of both the x and y components combined.
Understanding vector magnitudes helps to visualize and understand how forces are not just correlated to one direction, but act together to influence the object's speed and motion.
Acceleration Direction
The direction of the resultant acceleration is as significant as its magnitude. It tells us in which direction across the plane the object is accelerating. Rather than moving purely along the x or y axes, the object moves diagonally due to the combined effect of the force components.
We determine this direction using trigonometry, specifically the arctangent function. Use the formula \[ \theta = \arctan\left(\frac{a_y}{a_x}\right) \]. This tells us the angle the resultant vector forms with a given axis.
In our scenario, with \(a_x = 4.0 \text{ m/s}^2\) and \(a_y = 6.0 \text{ m/s}^2\), the direction is calculated as 56 degrees from the x-axis. This result shows not only the path of our object as it moves under total applied forces but helps visually predict where the object will likely move.

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Most popular questions from this chapter

A 20 -kg wagon is pulled along the level ground by a rope inclined at \(30^{\circ}\) above the horizontal. A friction force of \(30 \mathrm{~N}\) opposes the motion. How large is the pulling force if the wagon is moving with (a) constant speed and \((b)\) an acceleration of \(0.40 \mathrm{~m} / \mathrm{s}^{2}\) ?

A 600 -kg car is coasting along a level road at \(30 \mathrm{~m} / \mathrm{s}\). (a) How large a retarding force (assumed constant) is required to stop it in a distance of \(70 \mathrm{~m} ?(b)\) What is the minimum coefficient of friction between tires and roadway if this is to be possible? Assume the wheels are not locked, in which case we are dealing with static friction- there's no sliding. ( \(a\) ) First find the car's acceleration from a constant- \(a\) equation. It is known that \(\mathrm{v}_{i x}=30 \mathrm{v}_{f x},=0\), and \(x=70 \mathrm{~m}\). Use \(v_{k}^{2}=v_{u}^{2}+2 a x\) to find $$ a=\frac{v_{f x}^{2}-v_{i r}^{2}}{2 x}=\frac{0-900 \mathrm{~m}^{2} / \mathrm{s}^{2}}{140 \mathrm{~m}}=-6.43 \mathrm{~m} / \mathrm{s}^{2} $$ Now write $$ F=m a=(600 \mathrm{~kg})\left(-6.43 \mathrm{~m} / \mathrm{s}^{2}\right)-3858 \mathrm{~N} \text { or }-3.9 \mathrm{kN} $$ (b) Assume the force found in \((a)\) is supplied as the friction force between the tires and roadway. Therefore, the magnitude of the friction force on the tires is \(F_{\mathrm{f}}=3858 \mathrm{~N}\). The coefficient of friction is given by \(u=F_{f} / F_{N}\), where \(F_{N}\) is the normal force. In the present case, the roadway pushes up on the car with a force equal to the car's weight. Therefore, that $$ \begin{array}{l} F_{N}=F_{W}=m g=(600 \mathrm{~kg})\left(9.81 \mathrm{~m} / \mathrm{s}^{2}\right)=5886 \mathrm{~N} \\ \mu_{s}=\frac{F_{\mathrm{f}}}{F_{N}}=\frac{3858}{5886}=0.66 \end{array} $$ The coefficient of friction must be at least \(0.66\) if the car is to stop within \(70 \mathrm{~m}\).

A 900 -kg car is going \(20 \mathrm{~m} / \mathrm{s}\) along a level road. How large a constant retarding force is required to stop it in a distance of \(30 \mathrm{~m}\) ?

A 20 -kg wagon is pulled along the level ground by a rope inclined at \(30^{\circ}\) above the horizontal. A friction force of \(30 \mathrm{~N}\) opposes the motion. How large is the pulling force if the wagon is moving with (a) constant speed and \((b)\) an acceleration of \(0.40 \mathrm{~m} / \mathrm{s}^{2}\) ?

A 300 -g mass hangs at the end of a string. A second string hangs from the bottom of that mass and supports a 900 -g mass. \((a)\) Find the tension in each string when the masses are accelerating upward at \(0.700 \mathrm{~m} / \mathrm{s}^{2}\). Don't forget gravity. ( \(b\) ) Find the tension in each string when the acceleration is \(0.700 \mathrm{~m} / \mathrm{s}^{2}\) downward.

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