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Two vehicles are approaching an intersection. One is a 2500 -kg pickup traveling at 14.0 \(\mathrm{m} / \mathrm{s}\) from east to west (the \(-x\) -direction), and the other is a \(1500-\mathrm{kg}\) sedan going from south to north (the 1 y-direction at 23.0 \(\mathrm{m} / \mathrm{s} )\) (a) Find the \(x\) - and \(y-\) components of the net momentum of this system. (b) What are the magnitude and direction of the net momentum?

Short Answer

Expert verified
Net momentum components: \(-35000 \,\text{kg} \,\text{m/s}\) (x), \(34500 \,\text{kg} \,\text{m/s}\) (y). Net magnitude: \(49142.19 \,\text{kg} \,\text{m/s}\), direction: \(44.64^\circ\) north of west.

Step by step solution

01

Identify known values

For the pickup: mass \(m_1 = 2500\,\text{kg}\) and velocity \(v_{1x} = -14.0\,\text{m/s}\) since it's traveling in the \(-x\)-direction. For the sedan: mass \(m_2 = 1500\,\text{kg}\) and velocity \(v_{2y} = 23.0\,\text{m/s}\) in the \(+y\)-direction.
02

Calculate momentum components for each vehicle

The momentum of an object is given by the product of its mass and velocity. For the pickup, the momentum in the \(x\)-direction is \(p_{1x} = m_1 \cdot v_{1x} = 2500 \,\text{kg} \cdot (-14.0 \,\text{m/s}) = -35000 \,\text{kg} \, \text{m/s}\).For the sedan, the momentum in the \(y\)-direction is \(p_{2y} = m_2 \cdot v_{2y} = 1500 \,\text{kg} \cdot 23.0 \,\text{m/s} = 34500 \,\text{kg} \, \text{m/s}\).
03

Sum component momentums to find net momentum

The net momentum in the \(x\)-direction is simply \(p_{x, \text{net}} = p_{1x} = -35000 \,\text{kg} \, \text{m/s}\) since the sedan contributes no momentum in \(x\)-direction.The net momentum in the \(y\)-direction is \(p_{y, \text{net}} = p_{2y} = 34500 \, \text{kg} \, \text{m/s}\) since the pickup contributes no momentum in \(y\)-direction.
04

Calculate magnitude and direction of net momentum

The magnitude of the net momentum is found using the Pythagorean theorem: \(\sqrt{p_{x, \text{net}}^2 + p_{y, \text{net}}^2} = \sqrt{(-35000)^2 + (34500)^2} \, \text{kg} \, \text{m/s} = \sqrt{1225000000 + 1190250000} \, \text{kg} \, \text{m/s} = \sqrt{2415250000} \, \text{kg} \, \text{m/s} = 49142.19 \, \text{kg} \, \text{m/s}\).The direction is given by the angle \(\theta\) with the negative \(x\)-axis: \(\tan(\theta) = \frac{p_{y, \text{net}}}{|p_{x, \text{net}}|} = \frac{34500}{35000} = 0.9857\).Thus, \(\theta = \tan^{-1}(0.9857) = 44.64^\circ\) north of west.

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Key Concepts

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

Momentum Components
Momentum components break down an object's overall momentum into specific directions. In a two-dimensional setting as in this exercise, we consider both the x and y directions. This simplified approach makes it easier to analyze the momentum of each object separately. - Momentum is calculated by multiplying the mass of an object by its velocity. For instance, the pickup truck's momentum in the x-direction is given as: \[ p_{1x} = m_1 \cdot v_{1x} = 2500 \, \text{kg} \cdot (-14.0 \, \text{m/s}) = -35000 \, \text{kg} \, \text{m/s} \]- Similarly, for the sedan in the y-direction: \[ p_{2y} = m_2 \cdot v_{2y} = 1500 \, \text{kg} \cdot 23.0 \, \text{m/s} = 34500 \, \text{kg} \, \text{m/s} \]By focusing on momentum components, you can easily handle more complex scenarios of multidirectional motion.
Net Momentum
The net momentum is the combined momentum from all objects involved, found by adding the corresponding components together. In this exercise:- **Net momentum in the x-direction:** The pickup contributes with no additional x-momentum from the sedan. Therefore, \[ p_{x, \text{net}} = -35000 \, \text{kg} \, \text{m/s} \]- **Net momentum in the y-direction:** Only the sedan contributes, hence, \[ p_{y, \text{net}} = 34500 \, \text{kg} \, \text{m/s} \]These values show straightforward addition, where the directions of motion are orthogonal, making calculations easier. Net momentum offers a complete overview of how the momentum distributes across the system.
Pythagorean Theorem
The Pythagorean theorem helps find the magnitude of the net momentum when we have perpendicular momentum components. This is due to the property of right triangles:- We have the net momentum components: \[ p_{x, \text{net}} = -35000 \, \text{kg} \, \text{m/s} \] \[ p_{y, \text{net}} = 34500 \, \text{kg} \, \text{m/s} \]- The magnitude is: \[ \sqrt{p_{x, \text{net}}^2 + p_{y, \text{net}}^2} = \sqrt{(-35000)^2 + (34500)^2} \] \[ = \sqrt{1225000000 + 1190250000} \, \text{kg} \, \text{m/s} = 49142.19 \, \text{kg} \, \text{m/s} \]This method is vital for converting component momentums into a single usable value representing an object's total momentum.
Angle of Momentum
Determining the angle of momentum allows us to understand the direction of the resultant momentum vector with respect to a reference axis.- The angle \( \theta \) from the negative x-axis can be calculated using the inverse tangent function: \[ \tan(\theta) = \frac{p_{y, \text{net}}}{|p_{x, \text{net}}|} = \frac{34500}{35000} = 0.9857 \]- Solving for \( \theta \), we find: \[ \theta = \tan^{-1}(0.9857) = 44.64^\circ \]This angle is measured from the x-axis in a counter-clockwise direction, which in our scenario, translates to north of west. Calculating this angle allows us to fully understand the direction in which the combined momentum is acting.

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Most popular questions from this chapter

A railroad handcar is moving along straight, frictionless tracks with negligible air resistance. In the following cases, the car initially has a total mass (car and contents) of 200 \(\mathrm{kg}\) and is traveling east with a velocity of magnitude 5.00 \(\mathrm{m} / \mathrm{s} .\) Find the final velocity of the car in each case, assuming that the handcar does not leave the tracks. (a) A \(25.0-\mathrm{kg}\) mass is thrown sideways out of the car with a velocity of magnitude 2.00 \(\mathrm{m} / \mathrm{s}\) relative to the car's initial velocity. \((b) A 25.0-k g\) mass is thrown backward out of the car with a velocity of 5.00 \(\mathrm{m} / \mathrm{s}\) relative to the initial motion of the car. (c) A 25.0 \(\mathrm{kg}\) mass is thrown into the car with a velocity of 6.00 \(\mathrm{m} / \mathrm{s}\) relative to the ground and opposite in direction to the initial velocity of the car.

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