Unbalanced forces are really important when it comes to how things move. Here’s how they can change an object's speed and direction:

1. Acceleration: When there is an unbalanced force, it makes an object speed up or slow down. This is explained by Newton's second law, which tells us that: $F = ma$ Here, $F$ stands for the total force, $m$ is how heavy the object is, and $a$ is how fast the object is speeding up or slowing down.

   For example, if a force of 10 N pushes on a 2 kg object, it will speed up at $5 \, \text{m/s}^2$.

2. Direction Change: Unbalanced forces can also change where an object is going. Consider a car that goes around a curve. The force keeping the car on the curve is called centripetal force. It changes the car’s direction while it keeps moving at the same speed.

3. Speed Change: An unbalanced force can make an object go faster or slower. For instance, when something is sliding, the force of friction can slow it down. This is because friction works against the motion of the sliding object.

In short, unbalanced forces can change how fast an object is moving, where it is going, or both. They play a big part in how things move overall. Understanding these ideas fits well with what you learn in Year 9 Physics in Sweden.