Yah i got another question

a large crate is placed on the bed of a truck but is not tied down as the truck accelerates forward the crate slides across the bed until it hits the tailgate explain what causes this

i'm completley lost

Inertia causes this to happen. As the truck slams on the brakes, the crate will continue to move in the direction the truck was moving.

And what does Newtons First Law say about this?

When the truck accelerates forward, the crate tends to stay at rest due to inertia, which is the tendency of an object to resist changes in its motion. However, as the truck accelerates, a force is exerted on the crate, pushing it forward. Without any external forces acting on it, the crate will accelerate in the same direction as the truck. But, since there is no friction or mechanism to hold the crate in place on the truck's bed, it will start sliding in the opposite direction to what the truck is moving.

This sliding motion occurs because there is no net force to counteract the crate's inertia. The lack of friction or a securing mechanism allows the crate to move freely. As a result, the crate slides across the bed until it reaches the tailgate, where it finally stops due to the sudden change in direction where the tailgate acts as an obstruction.

When a large crate is placed on the bed of a truck without being tied down, it is not secured and can move freely. Therefore, when the truck accelerates forward, the crate experiences an external force from the truck's acceleration. This force causes the crate to slide across the bed of the truck until it hits the tailgate.

To understand this concept, we need to consider the basics of Newton's laws of motion. Newton's first law states that an object at rest will stay at rest, and an object in motion will stay in motion with the same speed and direction unless acted upon by an external force. In this scenario, the large crate is initially at rest but suddenly experiences a force when the truck accelerates forward. As a result, the crate tends to resist this change in motion due to its inertia.

Inertia is the property of an object to resist changes in its state of motion. Because the crate is not secured or tied down, it will tend to stay at rest due to its inertia. However, the accelerating truck exerts an external force on the crate, overcoming its inertia. The force between the crate and the bed of the truck is reduced due to friction, allowing the crate to slide across the bed.

Without any other external forces acting on the crate, it will continue to slide in the same direction as the truck's acceleration until it encounters an opposing force. In this case, the opposing force is the tailgate of the truck, which stops the crate's motion.

In order to prevent the crate from sliding, it is important to tie it down or secure it in place. This way, the crate will be able to resist the force of the truck's acceleration and remain in its original position on the bed of the truck.