Train cars are coupled together by being bumped into one another. suppose two loaded train cars are moving toward one another, the first having a mass of 150,000 kg and a velocity of 0.300m/s, and the second having a mass of 110,000 kg and a velocity of -0.120m/s. (the minus indicates direction of motion.) what is their final velocity?

0.122 m/s

Explanation:

mass of first train, m1 = 150,000 kg

initial velocity of first train, u1 = 0.3 m/s

mass of second train, m2 = 110,000 kg

initial velocity of second train, u2 = - 0.120 m/s

let the velocity of coupled mass after the collision is v.

Use the conservation of momentum

Momentum of trains before collision = Momentum of trains after collision

150000 x 0.3 - 110000 x 0.120 = (150000 + 110000)v

45000 - 13200 = 260000 v

31800 = 260000 v

v = 0.122 m/s

Thus, they travel with the speed of 0.122 m/s towards right after collision.

note: the given question is incomplete.

complete question is given below.

which is an example of kinetic energy?

a. the energy stored in ethanol  

b. a hockey puck sliding across the ice  

c. a compressed spring  

d. a ball sitting at the top of a ramp

solution: the kinetic energy is the energy posses by the virtue of the motion of the object.

in the given options, a, c and d are the example of potential energy because it is the energy posses by the virtue of the rest of the object. but option b has the kinetic energy as the object is in motion.

hence, a hockey puck sliding across the ice   is the apex example of kinetic energy.

so, the option (b) a hockey puck sliding across the ice   is the correct option.

the best answer for these questions would be:

1.            c. is smaller

2.            d) concrete operational

3.            b) interaction with the environment – the children interact with their environment can them learn more.

4.            a) parents who reason openly with children can limit a child’s cognitive ability.