A100. g iron rod is heated to an unknown initial temperature. while cooling down to a temperature of 25.0 degree c, the rod releases 600.2 j of energy. what was its initial temperature? (the specific heat of iron is 0.452 j/g degree c)

a) 38.3 j
b) 11.7 j
c) 27.7 j
d) 22.3 j

a)  

Explanation:

As we know that,  

where,

q = heat released  = -600.2 J

= mass of iron rod =100 g  

= final temperature =

= initial temperature = ?

= specific heat of iron =

Now put all the given values in equation, we get

Therefore, the initial temperature of iron rod was

(newtons first law)

conservation of momentum law states :

momentum before collision = momentum after collision

momentum p (kg-m/s)= mass * velocity

say moving car=1 000 kg, velocity = 10 m/s then p = 1 000*10= 10 000 kg-m/s

say still car = 2 000 kg, velocity = 0 m/s then p = 2 000* 0 = 0 kg-m/s

total momentum prior to collision = 10 000 + 0 = 10 000 kg-m/s

momentum after collision = 10 000 kg-m/s

mass now = 1 000 kg+2 000 kg = 3 000 kg

10 000 = 3 000 kg* velocity m/s

10 000/3 000 = velocity

3.33 m/s = velocity after collision

an impulse is a force applied over time , momentum is exclusive of external forces and a perfect collision is implied