Finding net force from acceleration, speed and distance

In summary: The power driving the railway engine is switched off. The engine stops, from its speed of 16m/s^-1, without braking in a distance of 1.1km.""Based on the hypothesis, calculate the mass of the railway engine."
  • #1
Lis277
7
0

Homework Statement


The power driving the railroad engine is switched off. The engine stops, from its speed of 16m/s^-1, without braking in a distance of 1.1km. A student hypothesis that the horizontal resistive force is constant. Based on the hypothesis, calculate the mass of the railway engine.

Homework Equations


Teacher didn't provide any relevant equations but i assume F=ma and vf^2-vi^2=2ad are important

The Attempt at a Solution


First i tried to find
acceleration

vf^2-vi^2=2ad
vf=0
vi=16
a=?
d=1.1
(0)^2-(16)^2=2(1.1)a
-256=2.2a
-116.36=a

I think the next step would be to find net force to plug all my variables into F=ma to find mass. I know net force is the total force on an object but I'm not sure how to find net force from my given variables.
 
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  • #2
Does it seem logical to you that an object that starts at 16 m/s and stops after 1.1 km can only have one possible mass?
 
  • #3
PS what would be the acceleration if the train stopped in 1.1m?
 
  • #4
PeroK said:
Does it seem logical to you that an object that starts at 16 m/s and stops after 1.1 km can only have one possible mass?
I would assume it only has one mass
 
  • #5
PeroK said:
PS what would be the acceleration if the train stopped in 1.1m?
a=-116.36?
 
  • #6
Lis277 said:
a=-116.36?
since acceleration is normally in the units of meters and i was given a distance in km, do i have to convert to m before plugging the distance in the equation to find acceleration?
 
  • #7
Lis277 said:
since acceleration is normally in the units of meters and i was given a distance in km, do i have to convert to m before plugging the distance in the equation to find acceleration?
What do you think?

Many distances could be 1.1 something. Inches, feet, yards, miles, light years, megaparsecs, angstrom units ...
 
  • #8
PeroK said:
What do you think?

Many distances could be 1.1 something. Inches, feet, yards, miles, light years, megaparsecs, angstrom units ...
acceleration would be 0.2327m/s
 
  • #9
Lis277 said:
acceleration would be 0.2327m/s
That looks a bit too big. How did you get that?
 
  • #10
PeroK said:
That looks a bit too big. How did you get that?
oops, made a mistake
vf^2-vi^2=2ad
vf=0
vi=16
a=?
d=1.1km-->1,100m
(0)^2-(16)^2=2(1100)a
-256=2200a
-0.11636m/s=a
 
  • #11
Lis277 said:
oops, made a mistake
vf^2-vi^2=2ad
vf=0
vi=16
a=?
d=1.1km-->1,100m
(0)^2-(16)^2=2(1100)a
-256=2200a
-0.11636m/s=a

Strictly speaking you should only really specify two significant digits and acceleration is ##m/s^2##.

On the other point, you can't know the mass without further data, as any vehicle could have this acceleration.
 
  • #12
PeroK said:
you can't know the mass without further data
I suspect that the intended additional data is either the power being developed by the engine before it was switched off, or maybe the tractive force. @Lis277 , please check you were not told either of these.
 
  • #13
haruspex said:
I suspect that the intended additional data is either the power being developed by the engine before it was switched off, or maybe the tractive force. @Lis277 , please check you were not told either of these.
Does the fact that the train is moving at a constant velocity make any difference?
 
  • #14
Lis277 said:
Does the fact that the train is moving at a constant velocity make any difference?
The train is not moving at a constant velocity. It is slowing down.

According to Google, context for the problem can be found at: https://www.coursehero.com/file/24013128/N11-B2p1Forcespdf/

"A total horizontal resistive force of 76kN acts on the railway engine."
 
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Related to Finding net force from acceleration, speed and distance

1. How do you calculate net force from acceleration, speed, and distance?

To calculate net force, you will need to use the equation F = m x a, where F is force, m is mass, and a is acceleration. You will also need to use the equation v = d/t, where v is speed, d is distance, and t is time. First, calculate the acceleration using the equation a = (v2 - v1) / t. Then, plug in the values for mass and acceleration into the equation F = m x a to find the net force.

2. Can you find net force without knowing the mass?

No, to calculate net force, you will need to know the mass of the object. Without knowing the mass, you will not be able to use the equation F = m x a to find the net force. However, you can still use the equation v = d/t to find the speed or the acceleration, which can be used to calculate the net force if the mass is known.

3. What is the unit of measurement for net force?

The unit of measurement for net force is Newtons (N). This is a derived unit in the International System of Units (SI) and is equivalent to 1 kg*m/s2. In other words, 1 Newton is the force required to accelerate 1 kilogram of mass at a rate of 1 meter per second squared.

4. How does increasing acceleration affect net force?

If acceleration increases, net force will also increase. This is because net force is directly proportional to acceleration, as shown in the equation F = m x a. This means that as the acceleration of an object increases, the net force acting on it will also increase. Similarly, if acceleration decreases, net force will also decrease.

5. Can you find net force if only given the distance traveled?

No, to calculate net force, you will need to know at least two of the following variables: mass, acceleration, and distance. If you are only given the distance traveled, you will not be able to find the net force. However, you can use the equation v = d/t to find the speed, and then use the equation a = (v2 - v1) / t to calculate the acceleration. With these values, you can then use the equation F = m x a to find the net force.

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