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This is my 3rd practice question that I don't know how to do :( Hoping peole can help me out, if someone could even work it out, would be greatly appriciated.

A skydiver, weighing 70kg, jumps from an aeroplane at an

altitude of 700 metres and falls for T1 seconds before pulling

the rip cord of his parachute. A landing is said to gentle if

the velocity on impact is no more than the impact velocity of

an object dropped from a height of 6 metres. The distance

that the skydiver falls during t seconds can be found from New-

ton’s Second Law, F = ma. During the free fall portion of

the the jump, we will assume that there is essentially no air

resistance, so F = −mg where g = 9.8ms^−2 and m = 70kg.

After the parachute opens, a significant drag term due to the

air resistance of the parachute affects the force F, causing the

force to become F = −mg − kv where v is the velocity and

k = 110kg/sec is a drag coefficient.

(a) Find the range of times T1 at which the rip cord can be

pulled for a gentle landing.

(b) Find the height after T1 seconds of free-fall.

A skydiver, weighing 70kg, jumps from an aeroplane at an

altitude of 700 metres and falls for T1 seconds before pulling

the rip cord of his parachute. A landing is said to gentle if

the velocity on impact is no more than the impact velocity of

an object dropped from a height of 6 metres. The distance

that the skydiver falls during t seconds can be found from New-

ton’s Second Law, F = ma. During the free fall portion of

the the jump, we will assume that there is essentially no air

resistance, so F = −mg where g = 9.8ms^−2 and m = 70kg.

After the parachute opens, a significant drag term due to the

air resistance of the parachute affects the force F, causing the

force to become F = −mg − kv where v is the velocity and

k = 110kg/sec is a drag coefficient.

(a) Find the range of times T1 at which the rip cord can be

pulled for a gentle landing.

(b) Find the height after T1 seconds of free-fall.

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