Kinetic Energy speed and a car

In summary, the original speeds of the two cars were v1 = v2 and v1 + 8.5 = v2 + 8.5. This was determined by setting up the conditions properly, where one car has twice the mass of the other and only half as much kinetic energy. By increasing their speeds by 8.5 m/s, both cars then have the same kinetic energy.
  • #1
fizz123
6
0
One car has twice the mass of a second car, but only half as much kinetic energy. When both cars increase their speed by 8.5 m/s, they then have the same kinetic energy. What were the original speeds of the two cars?

first i set it up like this:
.5 * m * v1^2 = .5 * (.5 * 2m * v2^2)

then i get:
v1 = v2

then
.5 * m * (v1 + 8.5)^2 = .5 * 2m * (v2 + 8.5)^2
.5 * (v1 + 8.5)^2 = (v2 + 8.5)^2

but its not right...
 
Physics news on Phys.org
  • #2
Set up your conditions properly!
1) "One car has twice the mass of a second car" [tex]m_{1}=2m_{2}[/tex]
2) "but only half as much kinetic energy" [tex]K_{1}=\frac{K_{2}}{2}[/tex]
3)"When both cars increase their speed by 8.5 m/s, they then have the same kinetic energy":
[tex]\frac{m_{1}}{2}(v_{1}+8.5)^{2}=\frac{m_{2}}{2}(v_{2}+8.5)^{2}, K_{1}=\frac{m_{1}}{2}v_{1}^{2},K_{2}=\frac{m_{2}}{2}v_{2}^{2}[/tex]

To help you along, we have:
[tex]K_{1}=\frac{2m_{2}}{2}v_{1}^{2}=\frac{m_{2}}{4}v_{2}^{2}=\frac{K_{2}}{2}[/tex]

Thus, we have: [tex]{v}_{1}=\frac{v_{2}}{2}[/tex]
 
Last edited:
  • #3
thank you, i got it now
 
  • #4
Howcome both masses are over 2?
 

Related to Kinetic Energy speed and a car

1. What is kinetic energy?

Kinetic energy is the energy that an object possesses due to its motion. It is directly proportional to the object's mass and the square of its velocity.

2. How is kinetic energy related to speed?

Kinetic energy is directly proportional to the square of an object's velocity. This means that as an object's speed increases, its kinetic energy also increases.

3. How does a car's speed affect its kinetic energy?

A car's kinetic energy is affected by its speed due to the direct relationship between speed and kinetic energy. As a car's speed increases, its kinetic energy also increases.

4. What is the formula for calculating kinetic energy?

The formula for calculating kinetic energy is KE = 1/2 * m * v^2, where KE is kinetic energy, m is the mass of the object, and v is the velocity or speed of the object.

5. How does kinetic energy impact a car's braking distance?

Kinetic energy plays a significant role in a car's braking distance. The higher the car's kinetic energy, the longer the braking distance will be. This is because more energy needs to be dissipated in order to slow down the car's motion.

Similar threads

  • Introductory Physics Homework Help
Replies
6
Views
1K
  • Introductory Physics Homework Help
Replies
5
Views
2K
  • Introductory Physics Homework Help
Replies
7
Views
970
  • Introductory Physics Homework Help
Replies
5
Views
754
  • Introductory Physics Homework Help
Replies
16
Views
2K
  • Introductory Physics Homework Help
Replies
1
Views
1K
  • Introductory Physics Homework Help
Replies
4
Views
525
  • Introductory Physics Homework Help
Replies
5
Views
751
  • Introductory Physics Homework Help
Replies
1
Views
2K
Replies
1
Views
664
Back
Top