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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
 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
 one year ago

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

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

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

applesjgtlBest ResponseYou've already chosen the best response.0
1/2(1200kg)(18.06m/s)^2=195698.16J
 one year ago

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

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

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

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

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

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