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The brakes in car A and car B stop working and they need to stop. Car A and car B have the same mass. Car A is traveling at 30 miles per hour, smashes into a big wall, and is brought to rest in a collision that lasts for a fraction of a second. Car B was also traveling at 30 mph but it drives out into a field of grasses and sand and finally comes to rest after a bumpy 20 second ride. Which car gets the larger impulse?

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Answer:

Both have equal impulse.

Explanation:

Let the mass of cars be m.

Then the Force acting on each of them for taking them to state of rest:

(Using Newton's second law of motion)

[tex]F_A=\frac{m\times (0-30)}{\Delta t_A}[/tex]

[tex]F_A=-30\frac{m}{\Delta t_A}[/tex] ...................................(1) (negative sign is associated with direction, here we are concerned about the magnitude only)

[tex]F_B=\frac{m\times (0-30)}{\Delta t_B}[/tex]

[tex]F_B=-30\frac{m}{\Delta t_B}[/tex] ...................................(2)

[tex]\because \Delta t_A<\Delta t_B[/tex]

[tex]\therefore F_A>F_B[/tex]

We know that impulse is given as:

[tex]J=F\times \Delta t[/tex] ........................................(3)

So, from eq. (1), (2) & (3)

[tex]J_A=F_A\times \Delta t_A[/tex]

[tex]J_A=-30m[/tex]

&

[tex]J_B=F_B\times\Delta t_A[/tex]

[tex]J_B=-30m[/tex]

Hence both have equal impulse.

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