Chapter 4: Problem 24
An object starts at \(x=x_{0}\) with a velocity \(v=v_{0}\) at the time \(t=t_{0}\) and moves with a constant acceleration \(a_{0}\). Show that the velocity \(v\) when the object has moved to a position \(x\) is \(v^{2}-v_{0}^{2}=2 a_{0}\left(x-x_{0}\right)\).
Short Answer
Expert verified
Use the work-energy theorem and simplify to show \(v^2 - v_0^2 = 2 a_0 (x - x_0)\).
Step by step solution
01
Understand the Problem
Identify the given variables and the relationship between them. The object starts at position \(x_0\) with velocity \(v_0\) and constant acceleration \(a_0\), and we need to find the velocity \(v\) when the object reaches position \(x\).
02
Recall Kinematic Equations
Remember that the equation for the velocity \(v\) at any time \(t\) given acceleration \(a_0\) is \(v = v_0 + a_0 t\).
03
Position Equation
Use the equation for the position \(x\) as a function of time: \[ x = x_0 + v_0 t + \frac{1}{2} a_0 t^2 \]
04
Solve for Time \(t\)
Isolate \(t\) in the position equation: \[ x - x_0 = v_0 t + \frac{1}{2} a_0 t^2 \]
05
Substitute and Eliminate \(t\)
Replace \(t\) in the velocity equation by solving the position equation for \(t\) and substituting it back. This can be complex algebraically, but let's use the work-energy theorem instead.
06
Work-Energy Theorem
Apply the work-energy theorem, which states: \[ \frac{1}{2} m v^2 - \frac{1}{2} m v_0^2 = F d \] where \(F = m a_0\) and \(d = x - x_0\), yielding \[ \frac{1}{2} m v^2 - \frac{1}{2} m v_0^2 = m a_0 (x - x_0) \]
07
Simplify the Equation
Cancel out the mass \(m\) on both sides of the equation: \[ \frac{1}{2} v^2 - \frac{1}{2} v_0^2 = a_0 (x - x_0) \]
08
Final Transformation
Multiply through by 2 to isolate \(v\) and get the final form: \[ v^2 - v_0^2 = 2 a_0 (x - x_0) \]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
constant acceleration
In physics, constant acceleration means an object's velocity changes at a consistent rate over time. When an object experiences constant acceleration, its speed increases by the same amount each second.
To describe this motion, we use kinematic equations that relate position, velocity, acceleration, and time. One such equation is:
\[ v = v_0 + a_0 t \]
Here:
For example, if you know the initial and final velocities, and the distance traveled, you can find the acceleration using algebraic manipulation.
To describe this motion, we use kinematic equations that relate position, velocity, acceleration, and time. One such equation is:
\[ v = v_0 + a_0 t \]
Here:
- \(v\) is the final velocity
- \(v_0\) is the initial velocity
- \(a_0\) is the constant acceleration
- \(t\) is the time elapsed
For example, if you know the initial and final velocities, and the distance traveled, you can find the acceleration using algebraic manipulation.
work-energy theorem
The work-energy theorem helps us understand the relationship between the work done on an object and its kinetic energy. The theorem states:
\[ \frac{1}{2} m v^2 - \frac{1}{2} m v_0^2 = F d \]
Here:
Let's connect this to our earlier problem. For an object with a constant acceleration \(a_0\), the force \(F\) is given by \(m a_0\) and the distance \(d\) is \(x - x_0\). Substitute these values into the work-energy theorem:
\[ \frac{1}{2} m v^2 - \frac{1}{2} m v_0^2 = m a_0 (x - x_0) \]
By cancelling out the mass \(m\), we get back to:
\[ \frac{1}{2} v^2 - \frac{1}{2} v_0^2 = a_0 (x - x_0) \]
and multiplying through by 2 results in:
\[ v^2 - v_0^2 = 2 a_0 (x - x_0) \]
\[ \frac{1}{2} m v^2 - \frac{1}{2} m v_0^2 = F d \]
Here:
- \(m\) is the mass of the object
- \(v\) is the final velocity
- \(v_0\) is the initial velocity
- \(F\) is the force applied
- \(d\) is the distance over which the force is applied
Let's connect this to our earlier problem. For an object with a constant acceleration \(a_0\), the force \(F\) is given by \(m a_0\) and the distance \(d\) is \(x - x_0\). Substitute these values into the work-energy theorem:
\[ \frac{1}{2} m v^2 - \frac{1}{2} m v_0^2 = m a_0 (x - x_0) \]
By cancelling out the mass \(m\), we get back to:
\[ \frac{1}{2} v^2 - \frac{1}{2} v_0^2 = a_0 (x - x_0) \]
and multiplying through by 2 results in:
\[ v^2 - v_0^2 = 2 a_0 (x - x_0) \]
algebraic manipulation
Algebraic manipulation is a crucial skill in physics, allowing us to rearrange and solve equations to find unknowns. Let's break down how we use algebra in our solution:
First, we used the kinematic equation for position:
\[ x = x_0 + v_0 t + \frac{1}{2} a_0 t^2 \]
We isolated \(t\) by rearranging terms:
\[ x - x_0 = v_0 t + \frac{1}{2} a_0 t^2 \]
While solving for \(t\) directly in this equation is complex, we used another method by applying the work-energy theorem.
Through algebraic steps, we substituted known values, and simplified:
\[ \frac{1}{2} m v^2 - \frac{1}{2} m v_0^2 = m a_0 (x - x_0) \]
We cancelled out the mass \(m\), making the equation simpler:
\[ \frac{1}{2} v^2 - \frac{1}{2} v_0^2 = a_0 (x - x_0) \]
Multiplying through by 2, we finally isolated the variable \(v^2\):
\[ v^2 - v_0^2 = 2 a_0 (x - x_0) \]
Algebraic manipulation thus helps in simplifying and solving complex physics problems by isolating and focusing on necessary variables.
First, we used the kinematic equation for position:
\[ x = x_0 + v_0 t + \frac{1}{2} a_0 t^2 \]
We isolated \(t\) by rearranging terms:
\[ x - x_0 = v_0 t + \frac{1}{2} a_0 t^2 \]
While solving for \(t\) directly in this equation is complex, we used another method by applying the work-energy theorem.
Through algebraic steps, we substituted known values, and simplified:
\[ \frac{1}{2} m v^2 - \frac{1}{2} m v_0^2 = m a_0 (x - x_0) \]
We cancelled out the mass \(m\), making the equation simpler:
\[ \frac{1}{2} v^2 - \frac{1}{2} v_0^2 = a_0 (x - x_0) \]
Multiplying through by 2, we finally isolated the variable \(v^2\):
\[ v^2 - v_0^2 = 2 a_0 (x - x_0) \]
Algebraic manipulation thus helps in simplifying and solving complex physics problems by isolating and focusing on necessary variables.