The figure given below shows the direction of the two forces P and Q acting on a skydiver :
Force P is caused by the gravity and force Q is caused by the friction
When the force P is bigger than the force Q, the speed of the skydiver remains the same
After the parachute opens, force P remains the same while force Q increases
After the parachute opens, force P decreases while force Q increases
Answer is Wrong!
Answer is Right!
This question was previously asked in
UPSC NDA-2 – 2024
Let’s analyze the options:
A) Force P is caused by the gravity and force Q is caused by the friction. This statement correctly identifies the source of the forces. P is gravity, and Q is air resistance, which is a form of fluid friction. This statement is correct.
B) When the force P is bigger than the force Q, the speed of the skydiver remains the same. If P > Q, there is a net downward force (P – Q). According to Newton’s Second Law (F_net = ma), this net force causes acceleration in the downward direction, meaning the speed will increase, not remain the same. This statement is incorrect.
C) After the parachute opens, force P remains the same while force Q increases. Force P is gravity (mg), which depends on the skydiver’s mass and the acceleration due to gravity. Opening a parachute does not significantly change the skydiver’s mass or gravity. Thus, P remains essentially the same. Air resistance (Q) depends on the skydiver’s speed, the density of the air, and the skydiver’s shape and size (drag coefficient and area). Opening a parachute dramatically increases the surface area and drag coefficient, causing the air resistance force Q to increase significantly at the same speed. This statement is correct.
D) After the parachute opens, force P decreases while force Q increases. As explained above, P (gravity) remains essentially the same. Q increases dramatically. This statement is incorrect because it says P decreases.
Both A and C are factually correct statements about the forces. However, MCQs typically have a single best answer. Option C describes a crucial dynamic event in skydiving (parachute deployment) and its direct impact on the forces and resulting motion, which is a common physics concept tested. Option A is a static identification of the forces. Given the options and the nature of physics questions regarding skydiving, Option C is likely considered the intended answer as it addresses a key change in the system’s dynamics.