4. A 9000 kg train car travelling at 4.5 m/s inellastically collides with a 7500 kg train car at rest. If all of the kinetic energy not conserved in this collision goes into increasing the internal energy of
the cars, how many Joules were absorbed?

91125Joules

Explanation:

Given data

M1= 9000 kg

U1= 4.5m/s

M2= 7500 kg

U1= 0 m/s

KE1= 1/2M1U1^2

KE1= 1/2*9000*4.5^2

KE1= 1/2*9000*20.25

KE1= 1/2*182250

KE1=91125joules

KE2= 1/2M2U2^2

KE1= 1/2*7500*0^2

KE1=0 joules

Hence the energy absorbed is

E= KE1-KE2

E= 91125-0

E= 91125Joules

the answer is the first electromagnet (a). this is because it has more coils around the ferromagnetic material. increasing the number of coils increases the surface area in which the metal interacts with the current in the coil. this enables more atoms in the metal to become aligned hence becoming more magnetized.