Final speed with mass, initial velocity, force, displacement

In summary, the problem involves a 1000kg car moving at 25 ms-1, with a net force of 200N acting to slow it down. The force acts through a distance of 300m. Using the equations for kinetic energy and velocity, the new speed is found to be 22.5 ms-1, with the correct answer being 25.0 ms-1. The discrepancy may be due to a mistake in calculation or a different unit used for the speed.
  • #1
TDizzl
12
0

Homework Statement


A 1000kg car is moving at 25ms when a net force of 200N acts to slow the car. This force acts while the car moves through a distance of 300m. Find the new speed.

Homework Equations


Kinetic Energy equation
v2=u2+2as

The Attempt at a Solution


Attempted the use of Kinetic Energy equation and v2=u2+2as
However the answer I get is 27.4 when the correct answer is 22.5
 
Last edited:
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  • #2
TDizzl said:

Homework Statement


A 1000kg car is moving at 25ms when a net force of 200N acts to slow the car. This force acts while the car moves through a distance of 300m. Find the new speed.

Homework Equations


Unknown

The Attempt at a Solution


Attempted the use of Kinetic Energy equation and v2=u2+2as
However the answer I get is 27.4 when the correct answer is 22.5
Why don't you show us your calculations?
 
  • #3
TDizzl said:

Homework Statement


A 1000kg car is moving at 25ms when a net force of 200N acts to slow the car. This force acts while the car moves through a distance of 300m. Find the new speed.

Homework Equations


Unknown

The Attempt at a Solution


Attempted the use of Kinetic Energy equation and v2=u2+2as
However the answer I get is 27.4 when the correct answer is 22.5
Are the relevant equations unknown to you? How did you solve the problem then?
You result is correct with the data you gave. Check if they are the same given in the original text. And do not forget the unit next time. What is the unit of the speed? Is it really ms?
 
  • #4
SteamKing said:
Why don't you show us your calculations?
W=Fd
=200*300
=60000
60000=½*1000*v2-½*1000*252
=500v2-312500
372500 = 500v2
v2=745
v=27.3
ehild said:
Are the relevant equations unknown to you? How did you solve the problem then?
You result is correct with the data you gave. Check if they are the same given in the original text. And do not forget the unit next time. What is the unit of the speed? Is it really ms?
Yea see for yourself, its a multiple choice question. And I changed the original post so it makes some sense.
 

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  • #5
TDizzl said:

Homework Statement


A 1000kg car is moving at 25ms when a net force of 200N acts to slow the car. This force acts while the car moves through a distance of 300m. Find the new speed.

Homework Equations


Kinetic Energy equation
v2=u2+2as

The Attempt at a Solution


Attempted the use of Kinetic Energy equation and v2=u2+2as
However the answer I get is 27.4 when the correct answer is 22.5
The force of 200 N is acting to slow the car, which is traveling initially at 25 m/s. If the force is acting to slow the car, it makes little sense to say that the car is going to speed up to 27.4 m/s. :oops:

Care to try again? I suggest you use F = ma here, in addition to v2=u2+2as
 
  • #6
SteamKing said:
The force of 200 N is acting to slow the car, which is traveling initially at 25 m/s. If the force is acting to slow the car, it makes little sense to say that the car is going to speed up to 27.4 m/s. :oops:

Care to try again? I suggest you use F = ma here, in addition to v2=u2+2as
Thanks, I managed to get the answer, all I done was
27.5-25=2.5
25-2.5=22.5
 
  • #7
TDizzl said:
W=Fd
=200*300
=60000
60000=½*1000*v2-½*1000*252
=500v2-312500
372500 = 500v2
v2=745
v=27.3

Yea see for yourself, its a multiple choice question. And I changed the original post so it makes some sense.

As the car slows down, the acceleration is negative. The force is opposite to velocity and displacement, so the work W is negative. You should have written W=Fd=-200*300= -60000 = 1/2mv2-1/2 m u2.

You changed the original post by changing the unit of speed from ms-1 to ms. Is it correct?
 
  • #8
The answer is correct as ms-1
 

1. How does mass affect the final speed?

The mass of an object does not directly affect its final speed. However, it does affect the amount of force needed to accelerate the object to a certain speed. The greater the mass, the more force is required to achieve the same final speed.

2. How does initial velocity impact the final speed?

The initial velocity of an object does impact its final speed. If the initial velocity is greater than the final velocity, the object will decelerate and its final speed will be lower. If the initial velocity is lower than the final velocity, the object will accelerate and its final speed will be higher.

3. What is the relationship between force and final speed?

According to Newton's Second Law of Motion, force is directly proportional to the acceleration of an object. Therefore, the greater the force applied to an object, the greater its acceleration and final speed will be.

4. Can displacement affect the final speed of an object?

Displacement does not directly affect the final speed of an object. However, displacement can indirectly impact the final speed by affecting the distance the object travels and the time it takes to reach its final speed. A greater displacement may result in a longer distance traveled and therefore a higher final speed.

5. Is there a formula for calculating final speed with mass, initial velocity, force, and displacement?

Yes, the formula is final speed = initial velocity + (force/mass) x displacement. However, this formula may not apply to all situations and may require adjustments for factors such as air resistance or friction.

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