Not sure why I can't use v=v0 + at on this problem. (2024)

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In summary, the conversation discusses the use of equations to determine the final velocity of a freight train that accelerates at a rate of 0.0400 m/s^2 for 8.00 min, starting with an initial velocity of 4.00 m/s. The first equation, v=v0 + at, is the correct equation to use and gives a final velocity of 23.2 m/s. The use of the second and third equations is considered roundabout and may result in incorrect calculations.

  • #1

remcalister

2
0

Homework Statement

Freight trains can produce only relatively small acceleration and decelerations.

(a) What is the final velocity of a freight train that accelerates at a rate of 0.0400 m/s^2 for 8.00 min, starting with an initial velocity of 4.00 m/s?

Homework Equations

v=v0 + at
x=x0 +v0t +1/2at^2
v^2=v0^2 +2a(x-x0)

The Attempt at a Solution

Why can't i use the first equation I listed to solve this problem? Using that equation, you end up with v = 76.8 m/s

If you first use the second equation, and then the third equation, you end up with v = 23.2 m/s

Thanks in advance!

  • #2

billy_joule

Science Advisor

1,200
331

The first eqn gives the same as the 2nd and third.

v = 76.8 m/s is wrong, 23.2 m/s is right you may have pressed a wrong button on your calculator.

v=v0 + at
v = 4 m/s + (0.04 m/s^2)*(8 min * 60s/min) = 23.2 m/s

  • #3

olivermsun

Science Advisor

1,268
136

The first equation is exactly what you're supposed to use. Using the second and third seems roundabout.

But how are you getting 76.8 m/s with the first equation? Can you show your work?

  • #4

remcalister

2
0

Oh goodness, it's been a long weekend haha. I accidentally set it up as 4 m/s TIMES (0.04m/s^2)(480s).

Thanks guys

  • #5

HalfLostAndSearching

1,008
0

As a scientist, it is important to understand the limitations of equations and when they can be applied. In this case, the equation v=v0 + at assumes that the acceleration is constant throughout the entire time period. However, in the problem given, it is stated that freight trains can only produce relatively small acceleration and decelerations. This means that the acceleration may not be constant and could change over time. Therefore, the equation v=v0 + at may not accurately represent the situation and it is necessary to use the more general equations x=x0 +v0t +1/2at^2 and v^2=v0^2 +2a(x-x0) to account for any changes in acceleration. These equations take into account the initial velocity, final velocity, and displacement, making them more appropriate for this problem. It is important to always carefully consider the given information and choose the appropriate equation to use in order to accurately solve a problem.

FAQ: Not sure why I can't use v=v0 + at on this problem.

What does the equation v=v0 + at represent?

The equation v=v0 + at represents the relationship between an object's initial velocity, its acceleration, and its final velocity after a certain amount of time has passed. It is known as the kinematic equation for constant acceleration.

Why can't I use the equation v=v0 + at for this problem?

There are several reasons why this equation may not be applicable to a certain problem. It is important to check the given information and ensure that the object has constant acceleration, the initial velocity is known, and the time interval is specified. Additionally, this equation does not account for other factors such as air resistance or changing forces.

What are some alternative equations that I can use?

Depending on the given information and the type of problem, there are several other kinematic equations that can be used instead of v=v0 + at. These include equations for displacement, final velocity, and time. It is important to choose the appropriate equation based on the given information and the unknown variable.

Can I use the equation v=v0 + at for objects with changing acceleration?

No, the equation v=v0 + at is only applicable for objects with constant acceleration. If the acceleration is changing, a different equation, such as the equation for average acceleration, should be used.

How can I check if I have correctly applied the equation v=v0 + at?

To ensure that the equation v=v0 + at has been correctly applied, you can check if the units of the equation match. The units for velocity are meters per second (m/s), the units for initial velocity are also meters per second (m/s), and the units for acceleration are meters per second squared (m/s^2). If the units do not match, then the equation has been incorrectly applied.

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                      Not sure why I can't use v=v0 + at on this problem. (2024)

                      FAQs

                      When to use v v0 at? ›

                      The velocity formula is used to calculate the final velocity of an object based on its initial velocity, acceleration, and time. It represents how an object's speed changes over time.

                      What does v v0 mean? ›

                      The first kinematic equation is v = v 0 + a t , where v is the final velocity, v 0 is the initial velocity, a is the constant acceleration, and t is the time.

                      How can I know when I should use the 3 equations of motion in problems? ›

                      The equations of motion, also known as SUVAT equations, are used when acceleration, a , is constant. They are known as SUVAT equations because they contain the following variables: s - distance, u - initial velocity, v - velocity at time t , a - acceleration and t - time.

                      How do you solve velocity problems? ›

                      To figure out velocity, you divide the distance by the time it takes to travel that same distance, then you add your direction to it. For example, if you traveled 50 miles in 1 hour going west, then your velocity would be 50 miles/1 hour westwards, or 50 mph westwards.

                      What is velocity v0? ›

                      The initial velocity, denoted as v0, is the velocity of an object at the beginning of its motion.

                      What is an example of accelerated motion? ›

                      Some uniformly accelerated motion examples include a ball rolling down a slope, a skydiver jumping out of a plane, a ball dropped from the top of a ladder and a bicycle whose brakes have been engaged.

                      What do the v0 represent? ›

                      To calculate the acceleration, we would say that a = (vf - v0) / t, where vf is the final velocity, and v0 is the initial, or starting velocity; t is the amount of time it takes for the velocity to change.

                      What is the formula for v0? ›

                      Expert-Verified Answer

                      The formula to solve for V0 is V0 = (V1-a)/t.

                      What is v0 in voltage? ›

                      The dc voltage at an output terminal with reference to a common terminal, normally ground, when no signal is applied to the input.

                      When can the equations of motion not be used? ›

                      Equation of motions are derived with assumption that accelaration is constant. We cannot use these equations if accelaration itself is changing.

                      What is velocity for dummies? ›

                      Velocity is the speed in a particular direction, and it is typically measured in meters per second (m/s or ms1). The difference between velocity and speed can be illustrated by a person walking around in a circle at a constant speed of 0.5 meters per second.

                      How do you write a velocity answer? ›

                      In the equation V = d/t, V is the velocity, d is the distance, and t is the time. Determine the object's acceleration by dividing the object's mass by force and multiply the answer by the time it took for it to accelerate.

                      What are the 4 formulas for velocity? ›

                      Motion with Constant Acceleration
                      VariableEquation
                      Velocityv=u+at
                      Displacement with positive accelerations=ut+21at2
                      Displacement knowing initial and final velocitiess=21(u+v)t
                      Velocity squaredv2=u2+2as

                      When the velocity v of a particle is given in terms of t? ›

                      The velocity v of a particle at time t is given by v=at+ b/t+ c where a,b,c are constants .

                      How do you know if velocity is initial or final? ›

                      Initial and Final Velocity

                      Initial velocity describes how fast an object travels when gravity first applies force on the object. On the other hand, the final velocity is a vector quantity that measures the speed and direction of a moving body after it has reached its maximum acceleration.

                      When can you say that a moving object is uniformly accelerating? ›

                      What is uniform acceleration? When an object is travelling in a straight line with an increase in velocity at equal intervals of time, then the object is said to be in uniform acceleration. Free falling of an object is an example of uniform acceleration.

                      When can you use Laplace's equation? ›

                      Laplace's equation, second-order partial differential equation widely useful in physics because its solutions R (known as harmonic functions) occur in problems of electrical, magnetic, and gravitational potentials, of steady-state temperatures, and of hydrodynamics.

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