Terminal Velocity
Terminal velocity is the fastest speed an object can travel at when it has resistive forces acting on it. You need to think about terminal velocity when it comes to accelerating cars, parachutists and sky divers, taking off aeroplanes, really any time of acceleration: it's why it is so hard to break land speed records.
We're going to look at a falling object:
We're going to look at a falling object:
When an object falls, initially the only force acting on it is gravity, its weight. As it starts to move, drag or resistance kicks in. Air resistance increases with speed and the object is accelerating, speeding up, so the air resistance will increase. As the air resistance increases, the acceleration of the object decreases because the resultant force is smaller. The object's speed is still increase just more slowly. Eventually there will come a point when the air resistance is the same size as the weight of the object. There is no resultant force so the object falls at a constant speed.
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Let's look at a slightly more complicated scenario now:
1) The person starts to fall. The only force acting on the object is gravity. The person accelerates. 2) As the person's speed increases, the air resistance increases so the acceleration decreases. The speed is still increasing, just more slowly. 3) Eventually, the air resistance equals the weight the person reaches their terminal velocity. 4) The person is traveling at a constant speed. 5) The person opens their parachute. The parachute has a large surface area and so the air resistance increases and their speed decreases rapidly. 6) As their speed decreases, the force of air resistance decreases. 7) The air resistance and weight are once again balanced so the parachutist reaches a new terminal velocity. 8) The person travels at a constant speed. |