College Physics II – Mechanics, Sound, Oscillations, and Waves
Definition
A seatbelt is a safety device designed to secure the occupant of a vehicle against harmful movement that may result from a collision or sudden stop. It reduces the force of impact and helps distribute the forces over stronger parts of the body.
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Seatbelts increase the time over which the force from a collision is applied, thereby reducing the impulse experienced by occupants.
They help in reducing linear momentum changes by restraining occupants and preventing them from being thrown forward at high velocity.
The effectiveness of seatbelts can be explained using Newton's First Law, where an object in motion stays in motion unless acted upon by an external force—in this case, the seatbelt provides that necessary force.
In collisions, seatbelts help spread out the forces across more resilient parts of the body like the pelvis and ribcage, minimizing injury.
The physics behind seatbelts involves concepts such as impulse ($Impulse = Force \times Time$) and conservation of momentum.
Review Questions
How do seatbelts reduce the impulse experienced by an occupant during a collision?
Explain how seatbelts help in distributing forces over stronger parts of the body during an accident.
Describe how Newton's First Law applies to passengers wearing seatbelts in a moving vehicle.
Related terms
Impulse: Impulse is defined as the product of force and time interval over which it acts on an object. It is also equal to the change in momentum.
Linear Momentum: Linear momentum is the product of an object's mass and its velocity. It is a vector quantity, possessing both magnitude and direction.
Conservation of Momentum: $\text{The principle stating that if no external forces act on a closed system}$ $\text{of objects, their total linear momentum remains constant before}$ $\text{and after any interaction.}$