Finding speed on kinetic energy question

[Tygra]

Hi all.

I have come across a question in the kenetic energy section on a physics classroom website. The question asks you to find the speed, and have given the energy output and mass. The energy is 12,000 joules and the mass 40kg.

The formula for calculating the kinertic energy is KE = 0.5 * m * v2.

The answer given states the speed is 24.5 m/s. Below is how they explain the question:

KE = 0.5*m*v2
12 000 J = (0.5) * (40 kg) * v2

300 J = (0.5) * v2

600 J = v2

v = 24.5 m/s


What I don't understand is where does the 600 come from. I see you sqaure root this figure to get the speed, but I cannot see how this figure comes from 12,000 J and 40kg. Obviously the 300 J comes from the 12,000 being divied by 40, I just need to see where the 600 comes from.

Thanks.

 

[Skrambles]

300 / 0.5 = 600

 

[Tygra]

Thanks, mate.

When I first glanced at that I was thinking 150. After some shock I finally understood it.

 

[GAURAV DUBEY]

Hello friend! explanation for your question is fine. Take care of physical units as well.

 

[asteriatic]

I would like to clarify the calculation process for finding speed using the kinetic energy formula. The formula, KE = 0.5 * m * v2, is used to calculate the kinetic energy of an object, where m is the mass of the object and v is its velocity. In this case, the given information is the kinetic energy (12,000 J) and the mass (40 kg). To find the velocity, we rearrange the formula to solve for v, which gives us v = √(2KE/m). Plugging in the values, we get v = √(2*12,000 J/40 kg). Simplifying this, we get v = √(600 J/kg). The 600 J/kg is not a random number, it is simply the result of dividing the given kinetic energy by the mass. Taking the square root of this gives us the velocity, which is 24.5 m/s. I hope this explanation helps clarify the calculation process.