Answer:
displacement at 45 s = 30
65 s = 50
So the average speed over the interval from 45 s to 65 s is
(50 - 30) cm / 20 s = 1 cm / sec
As a check an average speed of 1 cm / sec for 20 sec will produce a
displacement of 1 cm / sec * 20 sec = 20 cm or from 30 to 50 cm

When an opaque obstacle is placed between a source of light and a screen, a shadow of the obstacle is formed on the screen. The kind of shadow depends on the size of the source of light. In other words, the earth casts its shadow on the moon. The solar eclipse occurs when the moon comes between the sun and the earth.
If the resistor is in series with the rest of the circuit then a is the correct answer. The voltage across the resistor in series with another resistor is

where R is the big resistor and r is the small one and V is the total voltage drop across both. This is called a voltage divider
Answer:
Drag or air resistance
Explanation:
The force of friction caused by a moving fluid is called drag. When that fluid is air, it's also known as air resistance.