Question

A weight of 6 kg increases the speed of its force from 2 m / s to 4 m / s. By how many joules does the kinetic energy of the body increase?​

Answer 1

Answer:

36 J

Explanation:

Let's start off with the Kinetic Energy formula: 1/2m$v^{2}$

So to find the change in Kinetic Energy, you would first have to find the Kinetic Energy in the beginning and in the end.

*Note: Mass: you incorrectly wrote weight = 6 kg- because weight is a force you have to write 6 Newtons. If you are talking about the mass, you would write 6 kg. If you are talking about weight, you would write 6 Newtons. The difference will make significant changes to the answer, so I will give you the answer for both.

If 6 kg is the MASS:

Beginning: find the kinetic energy.

Plug in all parts of the formula: 1/2mv^2 = $\frac{1}{2}$(6)(2 squared)= $\frac{1}{2}$(6)(4)= 12 J

End: find the kinetic energy.

Plug in all parts of the formula: 1/2mv^2=$\frac{1}{2}$(6)(4 squared)=$\frac{1}{2}$(6)(16)= 48 J

Answer:

36 J

If 6 kg is the WEIGHT:

We know that the weight formula is mg, or mass times acceleration due to gravity (which is always 9.8 m/s^2). Plug in the numbers:

Weight = mass x acceleration due to gravity

6 = mass x 9.8

6 = 9.8m

*Divide both sides*

mass = 0.6 kg

Now, we can use the mass to find the kinetic energy.

Beginning: find the Kinetic Energy

Plug in all parts of the formula: 1/2mv^2 = $\frac{1}{2}$(0.6)(2 squared)= $\frac{1}{2}$(0.6)(4)= 1.2 J

End: find the Kinetic Energy

Plug in all parts of the formula: 1/2mv^2=$\frac{1}{2}$(0.6)(4 squared)=$\frac{1}{2}$(0.6)(16)= 4.8 J

Answer:

3.6 J

(this answer is not very feasible, so 36 J is the way to go. But just remember, don't mix up weight and mass again- as you can see, they lead to different answers!)