# Problem on Mechanics (Newton's law of motion)

• Christy0721
In summary, the conversation discusses a comment made by a student regarding an accident involving a big lorry and small car. The student correctly applies Newton's third law of motion to explain that both drivers experienced equal forces during the head-on collision, resulting in their serious injuries. However, the question of which force caused the injuries is raised, with the student and teacher discussing the different accelerations experienced by the two drivers during the crash. The conversation ends with the acknowledgement that the situation is unpredictable and the size and strength of the vehicles may affect the severity of injuries.
Christy0721

## Homework Statement

This question goes like this:
In an accident involving a big lorry and small car, the drivers of both vehicles were seriously injured. A student made a remark about the accident as follows: "A big lorry and a small car moved in the opposite directions and made a head-on collision. By Newton's third law of motion, the forces acting on both drivers are the same. As a result, both drivers were seriously injured."
Comment on the student's remark.

## Homework Equations

[F][/net]=ma
Third law: Whenever an object A exerts a force on another object B, B exerts a force of equal magnitude and opposite direction on A at the same time.

## The Attempt at a Solution

I think the student is correct. As the two vehicles collide head-on, they form an action-and-reaction pair. Therefore, both the lorry and the car receive the same magnitude of force exerted on them by each other.
What I'm not so sure about is which force caused the drivers' injury?
Is it because: the cars receive forces from opposite directions and this force causes the cars to stop abruptly, while the drivers still tend to move forward due to inertia. As a result, they hit the windscreens and get injured?
Like the teacher said this question is not that easy so I'm quite uncertain about my answer.

Heavy lorry hits light car - imagine the situation and describe in words what you think would happen .

Nidum said:
Heavy lorry hits light car - imagine the situation and describe in words what you think would happen .
I think the lorry with a larger mass would drive the light car backwards during the collision and the passenger in the light car would be more seriously injured. But this won't explain why the driver in the lorry is also seriously injured.

Christy0721 said:
I think the lorry with a larger mass would drive the light car backwards during the collision and the passenger in the light car would be more seriously injured. But this won't explain why the driver in the lorry is also seriously injured.

In reality anything can happen as the result of a head on crash . Roughly speaking though the bigger and stronger the vehicle you are in relative to the one crashing into you the less injuries you are are likely to receive .

Christy0721 said:
"A big lorry and a small car moved in the opposite directions and made a head-on collision. By Newton's third law of motion, the forces acting on both drivers are the same. As a result, both drivers were seriously injured."

It's a nonsense question really but think about the different accelerations experienced by the two drivers during the crash .

I know right my teacher likes raising silly questions lol
Thanks anyways

## 1. What are Newton's three laws of motion?

Newton's three laws of motion are:
1. An object will remain at rest or in uniform motion in a straight line unless acted upon by an external force.
2. The force acting on an object is equal to its mass times its acceleration.
3. For every action, there is an equal and opposite reaction.

## 2. How do Newton's laws apply to real-world situations?

Newton's laws can be applied to all types of motion, from objects moving at constant speeds to objects accelerating or changing direction. For example, when a person pushes a shopping cart, they are applying a force to the cart, causing it to accelerate. This is an example of Newton's second law.

## 3. What is inertia and how does it relate to Newton's first law?

Inertia is the tendency of an object to resist changes in its state of motion. Newton's first law states that an object will remain at rest or in uniform motion unless acted upon by an external force. This means that an object with more inertia will require a greater force to change its state of motion compared to an object with less inertia.

## 4. Can multiple forces act on an object at the same time?

Yes, multiple forces can act on an object at the same time. In fact, the net force on an object is the combination of all the forces acting on it. This is known as the principle of superposition.

## 5. How do you calculate the net force on an object?

The net force on an object can be calculated by adding together all the individual forces acting on the object. If the forces are acting in the same direction, they can be simply added together. If the forces are acting in different directions, they must be combined using vector addition.

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