That depends on the direction of the velocity (which the question doesn't say).
A electron has a negative charge. They represent energy levels.
An example of the use of an electron is the spherical shell. The larger the shell, the more energy the electron has.
Answer: 
Explanation:
According to the conservation of linear momentum principle, the initial momentum 
(before the collision) must be equal to the final momentum 
(after the collision):
(1)
In addition, the initial momentum is:
(2)
Where:
is the mass of the comet
is the mass of the asteroid
is the velocity of the comet, which is positive
is the velocity of the asteroid, since it is at rest
And the final momentum is:
(3)
Where:
is the final velocity
Then :
(4)
Isolating :
(5)
Finally:
This is the final velocity, which is also in the positive direction.
Answer:
Closed system, because the speed of the car is as expected in the case where an object has uniform acceleration for a time t
Explanation:
Here in the question it is mentioned that a toy car has an initial acceleration of 2m/s² across a horizontal surface so we can say that it is acted upon by an external force
Assuming that the acceleration is constant and the reason for this assumption is there at the last
The major difference between an open system and closed system is in case of open system there will be transfer of matter and in case of closed system there will be no change in matter of the system
If acceleration is constant in case of closed system we can expect the speed of the car after a time t by using the formula
s = u×t + 0·5×a×t²
where s is the distance travelled
t is the time taken to travel that distance
u is the initial velocity
a is the acceleration of that system
But in case of open system as there will be a change of mass there will be a change in velocity of the system so in this case we cannot expect the speed of the car after a time t
And if the acceleration is not constant then we cannot say that the toy car is an open system or closed system, that is why we are assuming that the acceleration of the toy car is constant
