High School

How much more kinetic energy does a 6-kilogram bowling ball have when it is rolling at 16 mph (7.1 meters per second) than when it is rolling at 14 mph (6.2 meters per second)?

Use the formula: [tex]KE = \frac{1}{2} mv^2[/tex]

A. 1.3 J
B. 35.9 J
C. 151.2 J
D. 266.5 J

Answer :

We start with the kinetic energy formula:

$$
KE = \frac{1}{2} m v^2,
$$

where $m$ is the mass and $v$ is the speed.

1. For the bowling ball with mass $m = 6\text{ kg}$ rolling at $v = 7.1\text{ m/s}$, the kinetic energy is calculated as:

$$
KE_1 = \frac{1}{2} \times 6 \times (7.1)^2.
$$

Evaluating the expression:

$$
(7.1)^2 \approx 50.41 \quad \text{and} \quad \frac{1}{2} \times 6 = 3,
$$

so

$$
KE_1 \approx 3 \times 50.41 = 151.23\text{ J}.
$$

2. For the ball rolling at $v = 6.2\text{ m/s}$, the kinetic energy is:

$$
KE_2 = \frac{1}{2} \times 6 \times (6.2)^2.
$$

Calculating further:

$$
(6.2)^2 \approx 38.44 \quad \text{and} \quad \frac{1}{2} \times 6 = 3,
$$

so

$$
KE_2 \approx 3 \times 38.44 = 115.32\text{ J}.
$$

3. The increase in kinetic energy when the bowling ball goes from $6.2\text{ m/s}$ to $7.1\text{ m/s}$ is found by the difference:

$$
\Delta KE = KE_1 - KE_2 \approx 151.23\text{ J} - 115.32\text{ J} = 35.91\text{ J}.
$$

Thus, the bowling ball has approximately $35.9\text{ J}$ more kinetic energy when rolling at $7.1\text{ m/s}$ compared to $6.2\text{ m/s}$.

The correct answer is $\boxed{35.9\text{ J}}$.

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