What effect does gravity have on the motion of a spacecraft according to the slingshot effect?

The slingshot effect, also known as gravity assist, utilizes the gravitational field of a celestial body to alter the speed and direction of a spacecraft. When a spacecraft approaches a planet, it falls towards the planet due to gravity, gaining speed as it does so. As the spacecraft swings around the planet, it can also gain additional speed by using the planet's orbital motion, effectively transferring some of the planet's momentum to the spacecraft.

The acceleration of the spacecraft occurs because it is drawn into the gravitational well of the planet, allowing it to move faster as it exits the gravitational influence. This technique is beneficial for missions requiring high speeds to reach distant destinations without expending additional fuel. By maximizing the gravitational pull of the planet, the spacecraft can achieve increased velocity, making it a crucial tool in space travel strategies.

In contrast, options related to slowing down or changing the trajectory without an increase in speed do not accurately capture the primary purpose and function of the slingshot effect regarding an increase in speed and efficiency of the spacecraft's journey.