How potential and kinetic energy changed during the spacecraft launches.
2 answers:
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The correct answer to the question is : 29.88 m.
EXPLANATION :
As per the question, the mass of the rock m = 50 Kg.
The rock is rolling off the edges of the cliff.
The final velocity of the rock when it hits the ground v = 24 .2 m/s.
Let the height of the cliff is h.
The potential energy gained by the rock at the top of the cliff = mgh.
Here, g is known as acceleration due to gravity, and g =
When the rock rolls off the edge of the cliff, the potential energy is converted into kinetic energy.
When the rock hits the ground, whole of its potential energy is converted into its kinetic energy.
The kinetic energy of the rock when it touches the ground is given as -
Kinetic energy K.E = .
From above we know that -
Kinetic energy at the bottom of the cliff = potential energy at a height h
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Hence, the height of the cliff is 29.88 m
Answer:
v= 4.0 m/s
Explanation:
- When standing on the bathroom scale within the moving elevator, there are two forces acting on Henry's mass: Normal force and gravity.
- Gravity is always downward, and normal force is perpendicular to the surface on which the mass is located (the bathroom scale), in upward direction.
- Normal force, can adopt any value needed to match the acceleration of the mass, according to Newton's 2nd Law.
- Gravity (which we call weight near the Earth's surface) can be calculated as follows:
- According to Newton's 2nd Law, it must be met the following condition:
- As the gravity is larger than normal force, this means that the acceleration is downward, so, we choose this direction as the positive.
- Solving for a, we get:
- We can find the speed after the first 3.8 s (assuming a is constant), applying the definition of acceleration as the rate of change of velocity:
- Now, if during the next 3.8 s, normal force is 930 N (same as the weight), this means that both forces are equal each other, so net force is 0.
- According to Newton's 2nd Law, if net force is 0, the object is either or at rest, or moving at a constant speed.
- As the elevator was moving, the only choice is that it is moving at a constant speed, the same that it had when the scale was read for the first time, i.e., 4 m/s downward.