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 one year ago
A 1200 kg racecar is driven along a frictionless horizontal surface at a speed of 65 km/hr. If a horizontal cord brings the car to rest in a distance of 2.2 m, what is the elasticity constant (k) of this spring?
 one year ago
A 1200 kg racecar is driven along a frictionless horizontal surface at a speed of 65 km/hr. If a horizontal cord brings the car to rest in a distance of 2.2 m, what is the elasticity constant (k) of this spring?

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Shane_B
 one year ago
Best ResponseYou've already chosen the best response.1Do you have any idea where to start?

Shane_B
 one year ago
Best ResponseYou've already chosen the best response.1I'd start by converting the velocity to m/s. Then calculate the KE of the racecar using:\[KE=\frac{1}{2}mv^2\]

Shane_B
 one year ago
Best ResponseYou've already chosen the best response.1Since the racecar comes to a rest you know that the change in KE will be the amount of work done on the car and: \[W=\frac{1}{2}kx^2\]

applesjgtl
 one year ago
Best ResponseYou've already chosen the best response.01/2(1200kg)(18.06m/s)^2=195698.16J

Shane_B
 one year ago
Best ResponseYou've already chosen the best response.1So:\[KE=\frac{1}{2}(1200kg)(18.06m/s)^2=195698J=Work\space done\]\[195698J=\frac{1}{2}k(2.2m^2)\]Now just solve for k.

Shane_B
 one year ago
Best ResponseYou've already chosen the best response.1Small correction there...it should have been:\[195698J=\frac{1}{2}k(2.2m)^2\]

applesjgtl
 one year ago
Best ResponseYou've already chosen the best response.0Oh, because it's not the unit that's being squared.

Shane_B
 one year ago
Best ResponseYou've already chosen the best response.1Looking at that last equation, what do you get for k?

Shane_B
 one year ago
Best ResponseYou've already chosen the best response.1It's a constant...no unit. You also have to consider significant figures in your calcs but that's how you solve it.

applesjgtl
 one year ago
Best ResponseYou've already chosen the best response.0Not overly concerned with significant figures in this case, but you make a good point. Thanks!
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