Question Video: Finding the Mass of a Body given Its Velocity and Kinetic Energy | Nagwa Question Video: Finding the Mass of a Body given Its Velocity and Kinetic Energy | Nagwa

# Question Video: Finding the Mass of a Body given Its Velocity and Kinetic Energy Mathematics • Third Year of Secondary School

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Find the mass of a body moving at 400 cm/s whose kinetic energy is 1184 joules.

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### Video Transcript

Find the mass of a body moving at 400 centimeters per second whose kinetic energy is 1184 joules.

We recall that the kinetic energy of any body can be calculated using the formula a half 𝑚𝑣 squared, where 𝑚 is the mass of the body and 𝑣 is its velocity. The standard units for these are kilograms and meters per second, respectively. And the standard units for kinetic energy are joules. We are told that the velocity is 400 centimeters per second, and we know there are 100 centimeters in one meter. This means that the velocity of the body is four meters per second. We are also told that the kinetic energy is 1184 joules.

Substituting these into our formula, we have 1184 is equal to a half multiplied by 𝑚 multiplied by four squared. Four squared is equal to 16, and multiplying this by a half gives us eight. Therefore, the right-hand side simplifies to eight 𝑚. We can then divide both sides of our equation by eight. This gives us 𝑚 is equal to 148. If a body with kinetic energy 1184 joules is moving at 400 centimeters per second, it has a mass of 148 kilograms.

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