Answer:
a.Attractive

Explanation:
When it comes to charges, the charges which are alike repel each other and the charges which are different will attract each other.
Here, there is a proton and electron which are different particles hence, they will attract each other.
= Charge of electron and proton = 
r = Distance between them = 997 nm
k = Coulomb constant = 
Force is given by

The force of attraction between the particles will be 
Answer:
Maximum speed of the car is 17.37 m/s.
Explanation:
Given that,
Radius of the circular track, r = 79 m
The coefficient of friction, 
To find,
The maximum speed of car.
Solution,
Let v is the maximum speed of the car at which it can safely travel. It can be calculated by balancing the centripetal force and the gravitational force acting on it as :


v = 17.37 m/s
So, the maximum speed of the car is 17.37 m/s.
Answer:
1. <--> A.
2. <--> C.
3. <--> D
4. <--> B.
explanation: i know my science!
(1) The image of an object placed further from the lens than the focal point will be upside down and smaller than the object.
(2) When light rays reflect, they bounce back.
(3) Images formed by a concave lens will look magnified.
(4) When light rays enter a different medium, they bend.
<h3>
1.0 Object placed further from the lens than the focal point</h3>
The image of an object placed further from the lens than the focal point will be diminished and inverted.
Thus, the correct answer will be "upside down and smaller than the object".
<h3>2.0 What is reflection of light?</h3>
The ability of light to bounce back when it strike a hard surface is known as refection.
<h3>3.0 Image formed by concave lens</h3>
A concave lens is diverging lens is usually virtual, erect and magnified.
<h3>4.0 Refraction of light</h3>
The change in speed of light when it travels from medium to another medium is known as refraction. Refraction is also, the ability of light to bend around obstacles.
Learn more about reflection and refraction of light here: brainly.com/question/1191238
Answer:

Explanation:
As we know that resistance of one copper wire is given as

here we know that

now we have


now we know that such 17 resistors are connected in parallel so we have


Now if a single copper wire has same resistance then its diameter is D and it is given as

now from above two equations we have


now we have
