Question

what is projectile of a javelin thrown at an angle of 30degrees from ground. air resistance is there as air has velocity of 10km/hr. force applied was 100N.

Answer 1

The trajectory is a non-parabolic curve due to air resistance and wind.

Answer 2

The question asks about the "projectile" of a javelin thrown under specific conditions. In physics, when discussing the motion of a thrown object, "projectile" refers to the object itself and its motion, particularly its trajectory (the path it follows).

The javelin, once thrown, is a projectile. Its motion is influenced by the forces acting upon it. In this case, the forces are:

1. Gravity: A constant force acting vertically downwards.
2. Air Resistance (Drag): A force opposing the motion of the javelin relative to the air. This force depends on the javelin's velocity relative to the air, its shape, size, and the air density.
3. Wind: The information "air has velocity of 10 km/hr" suggests the presence of wind. Wind is the motion of air itself. If there is wind, the air resistance force depends on the javelin's velocity relative to the wind. The wind also affects the motion by changing this relative velocity and potentially exerting a direct force depending on the javelin's orientation.

In the absence of air resistance and wind, the only force acting is gravity, and the trajectory of a projectile is a perfect parabola. However, the question explicitly states that air resistance is present and mentions air velocity (wind).

Due to the presence of air resistance, the trajectory of the javelin will deviate significantly from a parabola. The air resistance force always opposes the direction of motion relative to the air, causing the javelin to decelerate both horizontally and vertically. This results in:

• A shorter range compared to the ideal parabolic trajectory with the same initial velocity.
• A lower maximum height.
• An asymmetrical trajectory, where the descent is steeper than the ascent.

The wind (air velocity of 10 km/hr) further complicates the motion. If the wind is blowing in the direction of the throw (tailwind), it can increase the range. If it's blowing against the throw (headwind), it decreases the range. If it's a crosswind, it will cause the javelin to drift sideways. The air resistance force will depend on the javelin's velocity relative to the wind, which is $\vec{v}_{javelin} - \vec{v}_{wind}$.

The applied force of 100 N mentioned is the force used to launch the javelin, accelerating it to its initial velocity. This force is not acting during the flight. Without knowing the mass of the javelin and the details of the throwing motion (distance or time over which the force is applied), we cannot determine the initial velocity.

However, the question asks "what is projectile", likely referring to the trajectory. The trajectory is the path traced by the javelin. Given the conditions (gravity, air resistance, wind), the trajectory is a curved path that is not a parabola. It is a complex curve determined by the interplay of these forces, which often requires numerical methods to calculate precisely.

In summary, the projectile is the javelin itself, and its motion follows a trajectory. Due to air resistance and wind, this trajectory is a non-parabolic curve, lower and shorter than the ideal parabolic path, and asymmetrical.