1) Example of contact force: friction
2) Examples of non-contact forces: gravity and electromagnetic force
Explanation:
1)
Contact forces are forces that acts only when the objects involved are touching.
An example of contact force in the geosphere is friction. Friction is a force that acts when two objects slide past each other, and the surfaces of the two objects are in contact. Due to the presence of "microbumps" on the two surfaces, there is a resistive force opposing the motion of the two objects, and this force is called friction.
Friction also acts when an object is moving through a fluid, although it takes a different name: resistance. Also in this case, the resistance acts in the direction opposite to the motion of the object, slowing it down.
2)
Non-contact forces are forces that act from a distance, therefore they act even when the objects involved are not touching.
Examples of non-contact forces are:
- Gravitational force: this is an attractive force that acts between any object with mass. Its magnitude is directly proportional to the product of the masses of the two objects and inversely proportional to the square of the distance between the two objects.
- Electromagnetic force: this is a force exerted between electrically charged objects. Its magnitude is directly proportional to the product of the two charges and inversely proportional to the square of the distance between the charges. It can be attractive (if the charges have opposite sign) or repulsive (if the charges have same sign).
Learn more about forces:
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Answer:
The starting position of the runner.
Explanation:
When you look at the graph, you can see that the first point on the graph is twenty on the y-axis.
The runner starts at twenty, and ends at thirty.
Therefore, the runner starts at twenty on the y-axis, so it's the starting position of the runner.
Scientists can tell this by looking at seismic waves released by earthquakes. ( if you need me to elaborate more ask)
Answer:
The man moves across the ice with a speed of 0.345m/s.
Explanation:
From the conservation of linear momentum, we have that the total linear momentum before the book throw is equal to the total linear momentum just after it. Since the initial velocity of the system is zero (so the initial momentum is zero), we have that:
Where 
is the mass of the man, 
is the mass of the book, and 
and 
are their velocities. Plugging in the given values, we can compute the speed of the man (ignoring the negative sign, because we care about the magnitude, not the direction):
In words, the resulting speed of the man is 0.345m/s.
Answer:
Potential Energy
Explanation:
Potential energy is the energy stored in an object due to it's position relative to some zero position. An object possesses gravitational potential energy if it is positioned at a height above (or below) the zero height.
