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question 6
padded dashboards in automobiles are safer because the
momentum change is less
impulse is less
impact time is less
impact time is greater

Explanation:

Step1: Recall the impulse - momentum theorem

The impulse - momentum theorem is \(J=\Delta p\), where \(J = F\Delta t\) (impulse, \(F\) is the force, \(\Delta t\) is the time interval) and \(\Delta p\) is the change in momentum.

Step2: Analyze the situation of a collision

In a collision (e.g., a person hitting the dashboard), the change in momentum \(\Delta p\) (mass times the change in velocity) of the person is determined by the initial and final states of motion. For a given \(\Delta p\) (assuming the person comes to rest relative to the car in a collision), from \(J=\Delta p = F\Delta t\).

Step3: Consider the effect of padding

Padded dashboards increase the impact time \(\Delta t\). Since \(\Delta p\) is fixed (assuming the same initial and final velocities of the object in collision), from \(F=\frac{\Delta p}{\Delta t}\), when \(\Delta t\) increases, the force \(F\) (which can cause injury) decreases.

Answer:

impact time is greater