(a) Calculate the kinetic energy, in joules, of a 15-g bullet moving at 120 m/s.

Verified step by step guidance

1. Identify the formula for kinetic energy: \( KE = \frac{1}{2}mv^2 \), where \( m \) is the mass in kilograms and \( v \) is the velocity in meters per second.
2. Convert the mass of the bullet from grams to kilograms by dividing by 1000. For a 15-g bullet, the mass \( m = 0.015 \) kg.
3. Substitute the mass \( m = 0.015 \) kg and the velocity \( v = 120 \) m/s into the kinetic energy formula.
4. Calculate the expression \( \frac{1}{2} \times 0.015 \times (120)^2 \) to find the kinetic energy in joules.
5. Ensure the units are consistent and the calculation is correct to determine the kinetic energy in joules.

Key Concepts

Kinetic Energy Formula

Kinetic energy (KE) is the energy an object possesses due to its motion. It is calculated using the formula KE = 0.5 * m * v², where m is the mass in kilograms and v is the velocity in meters per second. This formula highlights the relationship between mass, velocity, and energy, indicating that kinetic energy increases with the square of the velocity.

Unit Conversion

In physics, it is often necessary to convert units to ensure consistency in calculations. In this question, the mass of the bullet is given in grams, which must be converted to kilograms (1 g = 0.001 kg) to use the kinetic energy formula correctly. Proper unit conversion is crucial for obtaining accurate results in scientific calculations.

Joules as a Unit of Energy

The joule (J) is the standard unit of energy in the International System of Units (SI). It is defined as the energy transferred when a force of one newton is applied over a distance of one meter. Understanding that kinetic energy will be expressed in joules helps in interpreting the results of the calculation and its relevance in physical contexts.