Answer:
B.
It will be greater than 10 J.
Explanation:
The total mechanical energy of an object is the sum of its potential energy (PE) and its kinetic energy (KE):
E = PE + KE
According to the law of conservation of energy, when there are no frictional forces on an object, its mechanical energy is conserved.
The potential energy PE is the energy due to the position of the object: the highest the object above the ground, the highest its PE.
The kinetic energy KE is the energy due to the motion of the object: the highest its speed, the largest its KE.
Here at the beginning, when it is at the top of the roof, the baseball has:
PE = 120 J
KE = 10 J
So the total energy is
E = 120 + 10 = 130 J
As the ball falls down, its potential energy decreases, since its height decreases; as a result, since the total energy must remain constant, its kinetic energy increases (as its speed increases).
Therefore, when the ball reaches the ground, its kinetic energy must be greater than 10 J.
The correct answer is A. Solid Rock
Answer:
1.93 m/s
Explanation:
Parameters given:
Mass = 4.5g = 0.0045kg
Spring constant = 8.0 N/m
Length of barrel = 13 cm = 0.013m
Frictional force = 0.035N
Compression = 5.8 cm = 0.058m
First, we find the P. E. stored in the spring:
P. E. = ½*k*x²
P. E. = ½ * 8 * 0.058² = 0.013J
Then, we find the work done by the frictional force while the sphere is leaving the barrel of the gun:
Work = Force * distance
The distance here is the length of the barrel.
Work = 0.035 * 0.13 = 0.0046 J
The kinetic energy of the sphere can now be found:
K. E. = P. E. - Work done
K. E. = 0.013 - 0.0046 = 0.0084J
We can now find the speed using the formula for K. E.:
K. E. = ½*m*v²
0.0084 = ½ * 0.0045 * v²
v² = 0.0084/0.00255 = 3.733
=> v = 1.93 m/s
Answer:
Temperature
Explanation:
Heat only flows from one point to the other due to the difference in temperature.
- Gravitational force depends only on mass and distance, not on the state of matter.
- The forces of attraction between molecules in matter are electromagnetic in nature, not gravitational.
- These attractive forces are stronger in a solid than in a liquid than in a gas.
- Gravitational forces between molecules is completely negligible compared to the em forces.
So, key answer is inter-molecular forces of solids is stronger than liquids.
