Conservation of momentum and energy: Self Test

Assuming that air friction is negligible, how much kinetic energy does it have when it hits the ground?  Calculate the answer yourself if you can.

Hint: First Calculate the potential energy at the top

Potential energy at top = weight • height

Remember weight = mass • gravity = mg

PE = mg • height

1. PE = 1($) kg • 2($) m/s² • 3($) m
2. PE = 4($) (kg • m/s²) • m
3. PE = 5($) newton • m
4. PE = 6($) joules

What is the speed of the rock just before it hits the ground (approximate your answer)? 7($) m/s

as impulse applied to an object is equal to the change in momentum of the object

Suppose a moving object collides with a stationary one and the two stick together.  How will the speed of the stuck-together objects compare to the speed of the original moving object?

One block of ice has a mass of 12 Kg and the other's mass is 18 kg.  The dynamite explodes.  If the block of lesser mass moves off with a speed of 10 m/s, what is the speed of the more massive block?

1($) m/s

Please type in the answer as it is wither it has a negative sign or not

If the two cars stick together, what is their speed immediately after the collision?

Hint: On both sides of the equation, you may use "pounds" for mass and "miles per hour" for velocity.  This is permissible because weight (pounds) is proportional to mass, and miles/hour is a legitimate unit of velocity.)

1($) miles/hour

How much work is done in holding a piano at shoulder height for 15 minutes if the piano weighs 1200 newtons and your shoulder is 1.5 meters above the ground?

The kinetic energy of the fast one is how many times as great as the kinetic energy of the slow one?

In 1($), kinetic energy is conserved, but in 2($), it is not.

1($) joules

approximate your answer without decimal points

1($) watts

From how high did it fall?

1($) meters

Hint: Since the object's mass does not matter, you may choose any mass you want. and do not forget to approximate to the nearest first decimal point.