Question

You and your friend are the rock toy competition your friend takes 8kg rock'n'roll it at the speed of three m/s you take a 3 kg rock and throw it at the speed 9 m/s which of the following has more kinetic energy anyway

Answer 1

To determine which object has more kinetic energy, we can use the kinetic energy formula:

\[
KE = \frac{1}{2} m v^2
\]

where \(m\) is the mass of the object and \(v\) is its velocity.

### For your friend's rock:
- Mass (\(m\)) = 8 kg
- Velocity (\(v\)) = 3 m/s

Calculating the kinetic energy for the friend's rock:

\[
KE_{friend} = \frac{1}{2} \times 8 \, \text{kg} \times (3 \, \text{m/s})^2
\]
\[
KE_{friend} = \frac{1}{2} \times 8 \times 9 = \frac{1}{2} \times 72 = 36 \, \text{Joules}
\]

### For your rock:
- Mass (\(m\)) = 3 kg
- Velocity (\(v\)) = 9 m/s

Calculating the kinetic energy for your rock:

\[
KE_{you} = \frac{1}{2} \times 3 \, \text{kg} \times (9 \, \text{m/s})^2
\]
\[
KE_{you} = \frac{1}{2} \times 3 \times 81 = \frac{1}{2} \times 243 = 121.5 \, \text{Joules}
\]

### Comparison:
- Kinetic energy of your friend's rock: **36 Joules**
- Kinetic energy of your rock: **121.5 Joules**

**Your rock has more kinetic energy.**