Falling safely

Question 1

what can frictional forces do (drag, friction, air

resistance)?

Answer 1

• act against the movement
  • lead to energy loss and inefficiency
  • can be reduced (shape, lubricant)

Question 2

Explain how objects falling through the Earth’s

atmosphere reach a terminal speed.

Answer 2

When objects fall through the Earth’s atmosphere they get faster and faster until they reach a speed where the upwards force (air resistance) and downwards force (weight) equal each other. At this point the object travels at its fastest speed called terminal speed.

Question 3

Understand why falling objects do not experience

drag when there is no atmosphere.

Answer 3

If there is no atmosphere there can be no air resistance (drag). This means that falling objects can not slow down.

Question 4

Understand that gravitational field strength or

acceleration due to gravity:

Answer 4

• is unaffected by atmospheric changes
• varies slightly at different points on the Earth’s
surface
• will be slightly different on the top of a mountain
or down a mineshaf

Question 5

what is acceleration due to gravity the same as?

Answer 5

same for any object at a given point on the Earth’s

surface.

Question 6

Explain, in terms of balance of forces, why objects

reach a terminal speed:

Answer 6

When the weight is bigger than the air resistance then the object speeds up. When the air resistance is bigger than the weight, then the object slows down. If the air resistance is the same as the weight then the forces are balanced and the object continues at the same speed.

Question 7

Explain in terms of the balance of forces how moving
objects:
• increase speed
• decrease speed
• maintain steady speed

Answer 7

• At the start, the object accelerates downwards because of its weight. There is no air resistance. There is a resultant force acting downwards.
• As it gains speed, the object’s weight stays the same, but the air resistance on it increases. There is a resultant force acting downwards.
• Eventually, the object’s weight is balanced by the air resistance. There is no resultant force and the object reaches a steady speed, called the terminal velocity.