Question

# A paraglider is flying horizontally at a constant speed.Assume that only two forces act on it in the vertical direction,its weight and a vertical lift

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A paraglider is flying horizontally at a constant speed.Assume that only two forces act on it in the vertical direction,its weight and a vertical lift force exerted on its wings by theair. The lift force has a magnitude of 1800 N.
(a) What is the magnitude and direction of the force that theparaglider exerts on the earth ?
(b)If the lift force should suddenly decrease to 1200 N, whatwould be the vertical acceleration of the glider ? For bothquestions, take the upward direction to be the + y direction.

2021-04-02

Let us assume that the skier is falling in the - y direction
The Lift force $$\displaystyle{F}_{{{l}{\quad\text{if}\quad}{t}}}={1800}{N}$$
There are two forces acting on him, 1) the Lift forceacting upwards
2) his wight acting downwards
The Net Force $$\displaystyle\sum{F}_{{{y}}}={m}{g}-{F}_{{{l}{\quad\text{if}\quad}{t}}}$$
According to Newton's second law, $$\displaystyle\sum{F}_{{{y}}}={m}{a}_{{{y}}}$$
Or $$\displaystyle{a}_{{{y}}}=\frac{{{m}{g}-{F}_{{{l}{\quad\text{if}\quad}{t}}}}}{{m}}$$
$$\displaystyle=\frac{{{m}{g}-{1800}}}{{m}}$$
Or $$\displaystyle{a}_{{{y}}}={g}-\frac{{1800}}{{m}}$$
b) If the vertical lift is reduced to 1200N, $$\displaystyle{a}_{{{y}}}={g}-\frac{{1200}}{{m}}$$