
In physics, motion is the phenomenon in which an object changes its position over time. Motion is mathematically described in terms of displacement, distance, velocity, acceleration, speed, and time. One can also speak of motion of images, shapes, and boundaries.
Movement of any object from one position to another position with respect to the observer is called as Motion. Motion Along a Straight Line: When an object moves along a straight line, the motion of the object is called rectilinear motion. For example; motion of a car on highway.
In physics, motion is the change in position of an object with respect to its surroundings in a given interval of time. Motion is mathematically described in terms of displacement, distance, velocity, acceleration, and speed. An object's motion cannot change unless it is acted upon by a force.

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Metal bar is aligned along East- West direction and it is dropped vertically down
So its velocity is along -Z direction,
Now the Earth's magnetic field is towards north so its towards +Y direction
now we have formula for force on a moving charge

v = - z direction
B = + y direction
now by the above formula


So force is towards East
so all positive charge is towards East end
The correct choice is
B. Double-replacement reactions
in this type of reaction , two ionic compounds react and swaps their cations or anions giving two new compounds in the product. hence the double replacement reactions does not deal with the nucleus. all other terms like strong nuclear forces, radioactivity and nuclear decay deal with the nucleus.
The force needed to overcome sliding friction is more than the force needed to overcome rolling friction or static or even fluid
Answer:
4 is the best option for it as there are some stuff in grade to ye