Answer: (C) The ball will accelerate to about 20 m/s.
Explanation: The ball is in free fall and no other but gravitational force acts on it. This means the ball will be subject to the gravitational acceleration, which is about 9.8 m/s^2. So after one additional second the ball will increase its velocity to (10+9.8) m/s = 19.8 m/s or approx. 20 m/s.
"Alice" is the one among the following choices given in the question that arrives at the other side first. the correct option among all the options that are given in the question is the first option or option "A". the other choices can be easily neglected. i hope that this is the answer that has come to your great help.
Force on left crate, right crate and truck we need to draw here
First we will write the equation for left crate


Now similarly for right crate

now for truck

Now we know that F = 200 N

now add all three equation



now we will find all tension using this value of acceleration



Answer:
Electric field at a point ( x , y , z) is
.
Explanation:
Given :
Electric potential in the region is , 
We need to find the electric field .
We know , electric field ,
{ Here r is distance }
In coordinate system ,
{
is partial derivative }
Putting all values we get ,

Hence , this is the required solution.
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