An student dropped their book from the top of a canyon into a river 40 meters below.

how long does it take for the book to hit the water?

2.0 s

2.9 s

4.3 s

Use this formula for an object starting from rest and accelerating:

Distance = (1/2) (acceleration) (time)²

In this problem, the distance is 40 meters, and acceleration is gravity.  

So . . .

40 m = (1/2) (9.8 m/s²) (time)²

Divide each side by  (4.9 m/s²) :

time² = (40 m) / (4.9 m/s²)

time² = 8.16 sec²

Take the square root of each side :

√(time²) = √(8.16 sec²)

time = 2.86 seconds

Round it to  2.9 sec (choice B)

answer: option c. i.e. electric current flowing “downhill” from the negative electrode to the positive electrode in a battery

explanation:

the water analogy to the circuits define the pipes (water flows) to the electric current. now, we know that the electric current flows from the positive terminal to the circuit (as shown in the diagram attached).

hence, option c is the correct answer.

a.metals can become magnetic if they have many spinning electrons that create magnetic fields.d.only some metals are attracted by magnets; these metals are called ferromagnetic.

d.wrapping an insulated wire around a metal with ferromagnetic properties and applying an electric current.