Answer:
Three machines that humans have created are the lever, the wheel, and the axle, and also a pulley. even though there's actually more. A lever is A rigid bar that is free to move around a fixed point, such as a screwdriver. The wheel and axle, everyone should know what that is and what it does, it lifts heavy objects, moves people quickly, and moves parts of a complex machine. Pulleys are used to lift things, pulleys can be used singly or with many pulleys working together in order to transport people or things. They can also be used to provide power from one shaft to another. ... Construction pulleys are used in order to lift and place heavy materials.
Answer:

ΔK = 2.45 J
Explanation:
a) Using the law of the conservation of the linear momentum:

Where:


Now:

Where
is the mass of the car,
is the initial velocity of the car,
is the mass of train,
is the final velocity of the car and
is the final velocity of the train.
Replacing data:

Solving for
:

Changed to cm/s, we get:

b) The kinetic energy K is calculated as:
K = 
where M is the mass and V is the velocity.
So, the initial K is:



And the final K is:




Finally, the change in the total kinetic energy is:
ΔK = Kf - Ki = 22.06 - 19.61 = 2.45 J
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