To determine what happens to the kinetic energy of a puppy weighing 3 kilograms, we need to use the kinetic energy equation:
[tex]\[
KE = \frac{1}{2} m v^2
\][/tex]
where [tex]\( m \)[/tex] is the mass of the puppy and [tex]\( v \)[/tex] is its velocity.
1. Calculate initial kinetic energy (KE_initial):
The mass of the puppy, [tex]\( m \)[/tex], is 3 kilograms. The initial velocity, [tex]\( v \)[/tex], is 2 meters per second.
[tex]\[
KE_{\text{initial}} = \frac{1}{2} \times 3 \times (2^2) = \frac{1}{2} \times 3 \times 4 = \frac{1}{2} \times 12 = 6 \text{ Joules}
\][/tex]
2. Calculate final kinetic energy (KE_final):
The final velocity, [tex]\( v \)[/tex], is 1 meter per second.
[tex]\[
KE_{\text{final}} = \frac{1}{2} \times 3 \times (1^2) = \frac{1}{2} \times 3 \times 1 = \frac{1}{2} \times 3 = 1.5 \text{ Joules}
\][/tex]
3. Determine the change in kinetic energy:
The change in kinetic energy, [tex]\( \Delta KE \)[/tex], is given by the difference between the final and initial kinetic energies.
[tex]\[
\Delta KE = KE_{\text{final}} - KE_{\text{initial}} = 1.5 \text{ Joules} - 6 \text{ Joules} = -4.5 \text{ Joules}
\][/tex]
Since the kinetic energy decreases, we also need to calculate the magnitude of the decrease:
[tex]\[
\text{KE decrease} = KE_{\text{initial}} - KE_{\text{final}} = 6 \text{ Joules} - 1.5 \text{ Joules} = 4.5 \text{ Joules}
\][/tex]
This tells us that her kinetic energy decreases by 4.5 Joules to a new value of 1.5 Joules.
Correct Answer:
A. Her kinetic energy decreases to 1.5 J.
