Answering 6th Grade Physics: Explaining School Bus Jerk Using Newton's Laws

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In summary, the passengers on a school bus are jerked backwards when the bus comes to a sudden stop because of Newton's First Law of Motion. This law states that an object at rest will remain at rest unless a force causes it to move, and an object in motion will remain in motion unless a force causes it to change its motion. In this case, the passengers are waiting for the bus seats to exert a force that will change their motion, causing them to be jerked backwards. This is also true for a sudden start, as objects in motion tend to stay in motion and objects at rest tend to stay at rest.
  • #1
shayes928
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The following question appeared on my son's 6th grade physics test recently:

"Why are passengers on a school bus jerked backwards when the bus comes to a sudden stop? Explain using Newton's laws of motion."

I was just wondering what a good answer to this might be.

Thanks in advance!
 
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6th grade?

The statement you wrote above is wrong though. The passesngers on the bus will NOT be jerked backward when the bus comes to a sudden stop.
Either they will be jerked forward when the bus comes to a stop (assuming the bus was moving forward to begin with), OR they will be jerked backward when the bus suddenly starts.


The answer lies in Newton's First Law of Motion: (Sixth grade version)
An object at rest will remain at rest unless a force causes it to move; AND an object in motion will remain in motion (at the same speed in a straight line) unless a force causes it to change its motion.

The passengers are not really "jerked." They simply remain in motion while the bus stops, or they remain at rest while the bus starts. The passengers are waiting for the bus seats to exert the force that will change their own motion.
 
  • #3
Because this schoolbus was traveling in reverse!

They are jerked backwards by a sudden start, not a sudden stop. Objects in motion tend to stay in motion; objects at rest tend to stay at rest. When the bus starts moving, the children tend to stay at rest, and are thus jerked back relative to the bus.

Njorl
 

1. What are Newton's Laws of Motion?

Newton's Laws of Motion are three physical laws that describe the relationship between an object's motion and the forces acting upon it. The first law states that an object will remain at rest or in motion with a constant velocity unless acted upon by an external force. The second law states that the force acting on an object is equal to its mass multiplied by its acceleration. The third law states that for every action, there is an equal and opposite reaction.

2. How do Newton's Laws apply to the jerking motion of a school bus?

The jerking motion of a school bus can be explained by Newton's first law of motion, also known as the law of inertia. The bus is initially in motion and wants to remain in motion, but when the brakes are applied suddenly, there is an external force acting on the bus. This causes the bus to slow down and the passengers inside to experience a jerking motion.

3. Can you explain the concept of inertia in relation to a school bus?

Inertia is the tendency of an object to resist changes in its state of motion. In the case of a school bus, the passengers inside have inertia and want to remain in motion with the bus. When the bus suddenly stops, the passengers continue to move forward due to their inertia until they are stopped by the seat belts or the seat in front of them.

4. How does the mass of a school bus affect its motion?

The mass of a school bus is directly related to its motion through Newton's second law of motion. The greater the mass of the bus, the more force is needed to accelerate or decelerate it. This is why larger and heavier vehicles, like school buses, require more force to change their motion compared to smaller and lighter vehicles.

5. How does understanding Newton's Laws of Motion help us in everyday life?

Understanding Newton's Laws of Motion can help us in everyday life by allowing us to predict and explain the motion of objects, including vehicles like school buses. It also helps us understand the importance of wearing seat belts to prevent injury in the event of sudden changes in motion. Additionally, it can be applied to various activities such as sports, driving, and even walking.

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