e the sat - physics

Question 1

What is the formula for arithmetic progression?

Answer 1

a + (n-1)d

Question 2

What is the formula for geometric progression?

Answer 2

ad^n

Question 3

What is the formula for arithmetic sequence?

Answer 3

n/2 (2a+(n-1)d)

Question 4

What is the formula for geometric sequence?

Answer 4

a(1-r^n)/1-r
or
a(r^n-1)/r-1

Question 5

What is the nCr formula?

Answer 5

n!/(n-r)!r!

Question 6

Describe the operation of a dc motor

Answer 6

Consists of a loop of wire in a perpendicular magnetic field formed by 2 magnets. When there is a current in the wire, it induces a magnetic field in the wire, the interaction between the magnetic field of the wire and the magnets causes the loop to experience a force. The force(s) experienced form a couple, so there is a turning effect - when the loop is at 90 degrees to the magnetic field, there is no force, so it does not rotate. The split ring commutator joined to the loop ensures it keeps spinning in the same direction.

Question 7

What are the factors that affect friction?

Answer 7

The velocity of the object (proportional)
The density of fluid (proportional)
Surface area of object (proportional)