Protons, neutrons, and electrons<span> are the three main subatomic particles found in an atom. Protons have a</span>positive<span> (+) </span>charge<span>. An easy way to remember this is to remember that both proton and </span>positive<span> start with the</span>letter<span> "</span>P<span>." Neutrons have no electrical </span>charge<span>.</span>
The contact force is indeed caused by "Contact".
Air resistance is basically a type of friction, which is apparently present providing two object contact.
The rest selections are all interaction force, which is not necessarily caused by contact.
Question :
If a body acquires a charge of -0.02 C, has it gained or lost electrons? Many?
Solution :
We know, charge gained is shown by negative sign.
Since, charged acquired is given as -0.02 C .
Therefore, it is body has gained electrons.
Now, number of electrons is given by :

Hence, this is the required solution.
Answer:
The force required to push to stop the car is 288.67 N
Explanation:
Given that
Mass of the car, m = 1000 kg
Initial speed of the car, u = 1 m/s
The car and push on the hood at an angle of 30° below horizontal, 
Distance, d = 2 m
Let F is the force must you push to stop the car.
According work energy theorem theorem, the work done is equal to the change in kinetic energy as :



The force required to push to stop the car is 288.67 N
Answer: B. 15.2s
Explanation: 600/39.5 = about 15.2