Question

A 20 kg curling stone is sliding in a positive direction at 4 m/s. A second curling stone is sliding at the same speed but in the opposite direction. What is the kinetic energy of the two stones?

Answer 1

Answer:

The kinetic energy of the two stones is 320 J

Explanation:

Kinetic energy is the energy that a body possesses due to its movement. So it is the capacity or work that allows an object to go from being at rest, or still, to moving at a certain speed.

In other words, the kinetic energy of an object is that which is produced due to its motion and depends on its mass and velocity as follows:

$Ec=\frac{1}{2} *m*v^{2}$

where the kinetic energy Ec is measured in joules (J), the mass m is measured in kilograms (kg) and the velocity v in meters/second (m/s).

In this case you know that a 20 kg curling stone is sliding in a positive direction at 4 m/s. So:

• m= 20 kg
• v= 4 m/s

Replacing you have:

$Ec_{1} =\frac{1}{2} *20 kg*(4\frac{m}{s}) ^{2}$

Ec₁= 160 J

A second curling stone slides at the same speed but in the opposite direction. So:

• m= 20 kg
• v= - 4 m/s

Replacing you have:

$Ec_{2} =\frac{1}{2} *20 kg*(-4\frac{m}{s}) ^{2}$

Ec₂= 160 J

The kinetic energy of the two stones is calculated as:

Ec= Ec₁ + Ec₂

Ec= 160 J + 160 J

Ec= 320 J

The kinetic energy of the two stones is 320 J