Falling safely

Question 1

All objects…

Answer 1

fall with the same acceleration due to gravity as long as the effect of air resistance is very small.

Question 2

The size of the air resistance force on a falling object depends on:

Answer 2

• Its cross-sectional area - the larger the area the greater the air resistance.
• Its speed - the faster it falls the greater the air resistance.

Question 3

Air resistance has a…

Answer 3

Significant effect on motion only when it is large compared to the weight of the falling object.

Question 4

Alternative use of parachutes

Answer 4

Drag racers and the Space Shuttle use parachutes to slow them down rapidly.

Question 5

Gravitational field strength

Answer 5

• The force on each kilogram of mass due to gravity, g = 10N/kg approximately on Earth.
• G is also known as acceleration due to gravity, g = 10 m/s² approximately.

Question 6

Explain what happens in the Diagram

Answer 6

• In part 1, the weight of the parachutist is greater than the air resistance. The parachutist accelerates displacing more air molecules every second. The air resistance force increases. This reduces acceleration. So, the higher the speed, the more air resistance.
• In part 2, the weight of the parachutist and air resistance are equal. The forces acting on him on him are balanced. He travels at a constant speed - terminal speed.
• In part 3, the air resistance is larger than the weight of the parachutist. It slows down and air resistance decreases. When the parachute opens, the upward force increases suddenly as there is a much larger surface area, displacing more air molecules every second. So, the larger the area, the more air resistance. The parachutist decelerates, displacing fewer air molecules each second, so the air resistance force decreases.
• In part 4, the parachutist reaches a slower terminal speed when his weight is equal to the air resistance once more, so he lands safety.

Question 7

The gravitational field strength:

Answer 7

• Is unaffect by atmospheric condition
• Varies with position on the earth’s surface (9.78 N/kg at the equator and 9.83 N/kg at the pole)
• Varies with height above or depth below the Earth’s surface.