A 88 kg fullback moving east with a speed of 5.0 m/s?

Question

is tackled by a 95 kg opponent running north at 3.0 m/s. If the collision is perfectly inelastic, calculate each of the following.

(a) the velocity of the players just after the tackle_____m/s

(b) the kinetic energy lost as a result of the collision_____J

and why is there energy missing?

stuk one this one guys- need help. Thanks ;)

Answer 1

Ok, let's just draw the x and y axiss.

Then the first ball is moving to the positive value of "x" with 5 m/s

then it's kinetic energy will be : 88*25 / 2 = 1100 Joules

The second ball is moving to the positive value of "y" with 3 m/s

then it's kinetic energy will be : 95*9 / 2 = 427.5 Joules

You know that even if it's a perfect inelastic colission, the linear momentum is constan :

m1*v1 + m2*v2 = (m1 + m2)*v

88*5 + 95*3 = 183*v

v = 3.96 m/s

for part b)

There is lost of energy, because, the energy IS ONLY CONSTANT, when you have an elastic collision, in other kinds of collisions you will have lost of energy, so then:

initial energy : 1100 Joules + 427.5 Joules = 1527.5 Joules

final energy : 183*3.96^2 / 2 = 1434.8 Joules

initial energy minus final energy = 92.7 Joules.

These are the answers.