Here's why:

* Inertia is the tendency of an object to resist changes in its motion. This means an object at rest wants to stay at rest, and an object in motion wants to stay in motion at the same speed and direction.

* Inertia is a property of mass. The more massive an object is, the harder it is to change its motion, meaning it has more inertia.

* Speed is a measure of how fast an object is moving.

Inertia only depends on the object's mass. No matter how fast an object is moving, it will take the same amount of force to change its motion, assuming its mass remains the same.

Think of it this way:

* A massive truck parked on a hill has a lot of inertia. It takes a lot of force to get it moving.

* That same truck moving at 60 mph still has the same inertia. It takes the same amount of force to stop it as it did to get it moving initially.

However, it's important to note that:

* Force is required to change speed. While inertia doesn't change with speed, you need force to accelerate or decelerate an object.

* Kinetic energy increases with speed. Even though inertia stays the same, a faster-moving object has more kinetic energy, which is the energy of motion. This means it can do more work if it collides with something.

Let me know if you have any other questions!