2. Kinematics

Question 1

Peter decides to go skydiving. From an altitude of 3500m, he falls off the aircraft. He attains terminal velocity before reaching an altitude of 800m. At the altitude of 800m, Peter opens his parachute. Assume that he falls vertically.

Describe qualitatively, with explanations, Peter’s motion after he fell from the aircraft, to the point where he attains terminal velocity.

Answer 1

Peter’s downwards acceleration decreases (velocity is increasing at a decreasing rate) as his weight remains the same whereas air resistance increases with increasing velocity. Hence, net force downwards decreases with time until he reaches terminal velocity where weight equals to air resistance.

Question 2

Define acceleration.

Answer 2

Acceleration is defined as the rate of change of velocity.

Question 3

Explain how it is possible for a body to undergo an acceleration although its speed remains constant.

Question 4

Define displacement.

Answer 4

Displacement of an object is its distance from a fixed point in a specific direction.

Question 5

Using the definition of displacement, explain how it is possible for a car to travel a certain distance and yet have zero displacement.

Answer 5

If a car travels a distance and ends up in its starting position,

Question 6

Peter decides to go skydiving. From an altitude of 3500 m, he falls off the aircraft. He attains terminal velocity before reaching an altitude of 800 m. At the altitude of 800 m, Peter opens his parachute. Assume that he falls vertically.

Describe qualitatively, with explanations, Peter’s motion after he fell from the aircraft, to the point where he attains terminal velocity.

Answer 6

Peter’s acceleration downwards decreases as the weight remains the same but air resistance increases with increasing velocity. Resulting in the net force downwards decreasing with time, till terminal velocity is reached when the weight is equal to the air resistance.