Answer:
Explanation:
Given
Each student exert a force of 
Let mass of car be m
there are 18 students who lifts the car
Total force by 18 students 
therefore weight of car 
mass of car 

(b)
Answer:
Option b. is correct
Explanation:
An RLC electrical circuit consists of constituent components: a resistor (R), an inductor (L), and a capacitor (C). A resistor, an inductor, and a capacitor are connected in series or parallel.
The impedances of the circuit elements depend on the frequency.
Both impedance magnitudes decrease when the frequency increases
Answer:
800 N
Explanation:
By Newton's third law which states that for every action, there is an equal and opposite reaction.
So, as the earth attracts the person towards its center, the person attracts the earth towards itself with the same magnitude of force but in the opposite direction.
Since the person is attracted towards the center of the earth by an 800 N gravitational force, the the earth is attracted toward the person with an 800 N reaction force.
<em>number of waves that pass a given point in one second is called <u>frequency..</u></em>