Answer:
c)the gravitational forces of people is so small it is overshadowed by that of earth.
Explanation:
The gravitational force between two objects is given by:
where
G is the gravitational constant
m1 and m2 are the masses of the two objects
r is the distance between the two objects
From the formula, we see that the gravitational force depends on the masses of the objects: since the mass of the Earth (
is much much larger than the average mass of one person (80-100 kg), then the gravitational force exerted by the Earth on a person is also much much larger than the gravitational force between two people.
Answer B. the direction of force is the same
The directions of magnetic force and magnetic field lines are shown in the figure.
The direction to find out the magnetic field lines is given by right hand curl rule. If the thumb shows the direction of current, then the curling fingers show the direction of magnetic field lines.
The direction of force can be given by right hand thumb rule, where
Thumb - Direction of magnetic field lines
Forefinger - Magnetic
force
Centre finger -
Current
Such that forefinger, centre finger and thumb must be at 90 degrees to each other.
The sound was repeated because of the phenomenon of echo. The speed of sound in the metal is 800 m/s.
Echo results from the reflection of sound waves. The reason why a sound may be heard twice owes to the phenomenon of reflection which leads to echo.
To determine the speed of sound in the metal;
Length of metal = 1000 m
Time taken between the two sounds = 2.5 s
Using the formula;
V = 2d/t
V = 2(1000)/2.5
V = 800 m/s
A water pipe freezes and cracks on a cold night. <em> (D)</em>
There are three physical changes going on in this scenario:
1). The air gets cold and dark at night.
2). The water in the pipe freezes and expands.
3). The pipe cracks.
There are no chemical changes in the description.
