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The initial velocity and acceleration of four moving objects at a given instant in time are given in the following table. Determine the final speed of each of the objects, assuming that the time elapsed since \(t=0 \mathrm{s}\) is \(2.0 \mathrm{s}\). $$ \begin{array}{lcc} \hline & \text { Initial velocity } v_{0} & \text { Acceleration } a \\ \hline \text { (a) } & +12 \mathrm{m} / \mathrm{s} & +3.0 \mathrm{m} / \mathrm{s}^{2} \\ \text { (b) } & +12 \mathrm{m} / \mathrm{s} & -3.0 \mathrm{m} / \mathrm{s}^{2} \\\ \text { (c) } & -12 \mathrm{m} / \mathrm{s} & +3.0 \mathrm{m} / \mathrm{s}^{2} \\\ \text { (d) } & -12 \mathrm{m} / \mathrm{s} & -3.0 \mathrm{m} / \mathrm{s}^{2} \\\ \hline \end{array} $$

Short Answer

Expert verified
Final velocities: (a) 18 m/s, (b) 6 m/s, (c) -6 m/s, (d) -18 m/s.

Step by step solution

01

Identify Known Values

For each object, identify the given values from the table: initial velocity \(v_0\), acceleration \(a\), and time \(t = 2.0\,s\).
02

Apply the Final Velocity Formula

Use the kinematic equation for final velocity: \(v = v_0 + a \, t\). This formula will allow us to calculate the final velocity for each object.
03

Calculate Final Velocity for Object (a)

With \(v_0 = +12 \, \mathrm{m/s}\), \(a = +3.0 \, \mathrm{m/s^2}\), and \(t = 2.0 \, \mathrm{s}\): \(v = 12 + 3.0 \times 2.0 = 18 \, \mathrm{m/s}\).
04

Calculate Final Velocity for Object (b)

With \(v_0 = +12 \, \mathrm{m/s}\), \(a = -3.0 \, \mathrm{m/s^2}\), and \(t = 2.0 \, \mathrm{s}\): \(v = 12 - 3.0 \times 2.0 = 6 \, \mathrm{m/s}\).
05

Calculate Final Velocity for Object (c)

With \(v_0 = -12 \, \mathrm{m/s}\), \(a = +3.0 \, \mathrm{m/s^2}\), and \(t = 2.0 \, \mathrm{s}\): \(v = -12 + 3.0 \times 2.0 = -6 \, \mathrm{m/s}\).
06

Calculate Final Velocity for Object (d)

With \(v_0 = -12 \, \mathrm{m/s}\), \(a = -3.0 \, \mathrm{m/s^2}\), and \(t = 2.0 \, \mathrm{s}\): \(v = -12 - 3.0 \times 2.0 = -18 \, \mathrm{m/s}\).

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Key Concepts

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

Final Velocity
In kinematics, the concept of final velocity is crucial to understanding motion. Final velocity refers to the speed and direction an object possesses at the end of a period of acceleration. It is denoted by the symbol \( v \). To determine the final velocity, we use the kinematic equation: \[ v = v_0 + a \, t \] Where:
  • \( v \) is the final velocity
  • \( v_0 \) is the initial velocity
  • \( a \) is the acceleration
  • \( t \) is the time elapsed
This equation helps us predict how the speed of an object will change over time, considering its initial speed and the impact of any forces causing acceleration. It's important to note that both initial velocity and acceleration can be positive or negative, indicating direction. Positive and negative values will directly affect the outcome of the final velocity. Knowing how to calculate final velocity is essential in analyzing motion accurately. Let's explore further by understanding the components of this formula.
Initial Velocity
Initial velocity is the speed and direction an object starts moving with when observed in a problem. In the equation for final velocity \( v = v_0 + a \, t \), the term \( v_0 \) represents the initial velocity. It serves as the starting point for calculations involving motion, allowing us to predict how much an object's speed will change under acceleration over a specified time period.To comprehend this concept better, consider these key points:
  • Initial velocity is crucial for setting the stage for any motion analysis.
  • It can be measured in various units, but meters per second (m/s) is standard in kinematics.
  • The sign of the initial velocity (+ or -) indicates its initial direction.
By understanding the initial velocity, one can effectively track changes in motion and how they relate to other parameters, such as acceleration. Initial conditions are vital for understanding the dynamics of an object's movement.
Acceleration
Acceleration describes how quickly an object's velocity is changing and in what direction. It plays a crucial role in kinematics by dictating how speed or direction changes over time. In the equation \( v = v_0 + a \, t \), \( a \) stands for acceleration, and it profoundly affects the object's final velocity.Here are some essential points about acceleration:
  • Acceleration is often measured in meters per second squared (m/s²).
  • A positive acceleration means the object is speeding up in its initial direction.
  • A negative acceleration or deceleration means the object is slowing down or speeding up in the opposite direction.
  • Zero acceleration indicates constant velocity.
Understanding acceleration allows us to make informed predictions about an object's motion over time. Knowing whether forces acting on an object increase or decrease its speed or alter its direction of motion is key to solving kinematic problems effectively.

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Most popular questions from this chapter

A cart is driven by a large propeller or fan, which can accelerate or decelerate the cart. The cart starts out at the position \(x=0 \mathrm{m}\), with an initial velocity of \(+5.0 \mathrm{m} / \mathrm{s}\) and a constant acceleration due to the fan. The direction to the right is positive. The cart reaches a maximum position of \(x=+12.5 \mathrm{m},\) where it begins to travel in the negative direction. Find the acceleration of the cart.

Two soccer players start from rest, \(48 \mathrm{m}\) apart. They run directly toward each other, both players accelerating. The first player's acceleration has a magnitude of \(0.50 \mathrm{m} / \mathrm{s}^{2}\). The second player's acceleration has a magnitude of \(0.30 \mathrm{m} / \mathrm{s}^{2}\). (a) How much time passes before the players collide? (b) At the instant they collide, how far has the first player run?

One afternoon, a couple walks three-fourths of the way around a circular lake, the radius of which is \(1.50 \mathrm{km}\). They start at the west side of the lake and head due south to begin with. (a) What is the distance they travel? (b) What are the magnitude and direction (relative to due east) of the couple's displacement?

A motorcycle has a constant acceleration of \(2.5 \mathrm{m} / \mathrm{s}^{2} .\) Both the velocity and acceleration of the motorcycle point in the same direction. How much time is required for the motorcycle to change its speed from. (a) 21 to \(31 \mathrm{m} / \mathrm{s},\) and (b) 51 to \(61 \mathrm{m} / \mathrm{s} ?\)

(a) What is the magnitude of the average acceleration of a skier who, starting from rest, reaches a speed of \(8.0 \mathrm{m} / \mathrm{s}\) when going down a slope for \(5.0 \mathrm{s} ?\) (b) How far does the skier travel in this time?

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