What is the approximate escape velocity from Earth's surface?

What is the approximate escape velocity from Earth's surface?

• A. 7.9 km/s
• B. 9.8 km/s
• C. 11.2 km/s
• D. 15.0 km/s

Answer: (C)

The escape velocity from Earth's surface is approximately 11.2 km/s. This value represents the minimum speed an object must reach to break free from Earth's gravitational influence without any further propulsion.

To understand why this speed is necessary, consider that as an object moves away from Earth, it must overcome the gravitational pull that tries to pull it back. The escape velocity is derived from the balance between kinetic energy (the energy of motion) and gravitational potential energy (the energy stored due to position in a gravitational field). At around 11.2 km/s, the kinetic energy of the object is sufficient to equal the gravitational potential energy, allowing it to escape into space.

Other choices do not correctly represent the escape velocity for Earth. The value of 7.9 km/s, for example, may refer to the velocity required to achieve low Earth orbit rather than escaping Earth's gravity entirely. Similarly, 9.8 km/s is roughly the average speed of a projectile when launched upwards under Earth’s gravitational force, but it does not account for the energy needed to escape entirely. Finally, 15.0 km/s exceeds the escape velocity and suggests unnecessary excess speed that would not be required for just escaping Earth's gravitational field. Thus, the most accurate approximation of