Two cars collide, find temperature change

AI Thread Summary
Two cars collide head-on at 80 km/hr, converting their kinetic energy into thermal energy. The kinetic energy formula K = 0.5mv^2 is used to calculate the total energy, resulting in K = 492.8m after converting speed to meters per second. The heat transfer equation Q = cm(delta T) is applied, but the user mistakenly calculates a change in temperature rather than an absolute temperature. The discussion reveals confusion about unit conversion and the correct application of temperature change, with the user seeking clarification on their calculations. The final temperature increase remains unresolved, indicating further assistance is needed.
Flip18064
Messages
7
Reaction score
0

Homework Statement



Two cars collide head on while each is traveling at 80 km/hr. Suppose all their kinetic energy is transformed into the thermal energy of the wrecks. What is the temperature increase of each car? (Assume each car's specific heat is that of iron)

Homework Equations



K = .5mv^2
Q = cm(delta T)
iron specific heat = .449 J/(g*K)

The Attempt at a Solution



K = 2(.5m(22.2)^2) = 492.8m

(converted 80 km/hr to m/s)

Q = 492.8m = (.449)(2m)T
T = 548.8 K
= 275.6 C

Which is the wrong answer. I don't know what i am doing wrong. Can someone please help me. Thanks
 
Physics news on Phys.org
Well, for one, there is no reason to convert your units. You calculated a \Delta T, not a temperature, and \Delta °C = \Delta K. Is the correct answer 549.9 K?
 
Oh yeah, I see what your saying. However 549 is still the wrong answer, so i must be doing something else wrong too.
 
Can anyone help me? I am really stuck...
 

Thread 'Struggling to understand the concept of this question (ice cube in water optics question)'

TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
View full post »
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
View full post »

Similar threads

What is the Temperature Increase of Cars Colliding at 80 km/hr?
Replies
1
Views
3K
Change in temperature of air in a closed system
Replies
16
Views
2K
Change in Entropy When Mixing Water at Different Temperatures
Replies
5
Views
1K
Find rate of temperature change using heat capacity, density and area
Replies
4
Views
2K
Thermodynamics - Change in Temp
Replies
2
Views
1K
Calorimetry - finding the final temperature of a system of ice and water
Replies
7
Views
2K
Water temperature with two materials cooling it
Replies
7
Views
1K
Transforming kinetic energy into thermal energy
Replies
2
Views
27K
Change in temperature for a system with entropy change
Replies
4
Views
2K
Heat Question -- Temperature rise of a hiker on a long hike
Replies
1
Views
2K

Hot Threads

Recent Insights

Back
Top