A stone was projected at an angle of 40o and initial velocity of 20m/s. (a.)Determine the time of flight  (b)Maximum height.

A.) 1.3 seconds

B.) 0.42 m

Explanation:

A.) You are given the angle of projection to be 40 degrees and initial velocity of 20m/s. 

At vertical component

U = Usin 40 that is,

U = 20sin40

Using the first equation of motion under gravity

V = U - gt

Let V = 0

0 = UsinØ - gt

gt = UsinØ

t = UsinØ/g

Where U = 20 m/s

Ø = 40 degree

g = 9.8 m/s^2

Substitutes all the parameters into the formula

t = 20sin40/9.8

t = 1.3 seconds

Total time of flight T = 2t

T = 2 × 1.3 = 2.6 s

B.) To calculate the maximum height,

You will use the formula

V^2 = U^2 - 2gH

At maximum height, V = 0

2gH = Usin^2Ø

H = Usin^2Ø/ 2g

Substitutes all the parameters into the formula

H = 20 sin^2(40) ÷ 2(9.8)

H = 8.2635/19.6

H = 0.42 m

air exerts forces on falling objects near earth’s surface.

explanation:

the term 'free falls' refer to object that are falling towards the earth, in a situation in which gravity is the only force acting on the object.

for an object in free fall, the acceleration is constant (g, the gravitational acceleration), and so the velocity of the object constantly increases.

for objects near earth's surface, there is always another force acting on the object: the resistance due to the air. this force is opposed to the direction of fall of the object, and it is proportional to the velocity of the object, so as the object falls down, this force increases up to a point when it balances the force of gravity, and the object continues its motion at constant velocity (called terminal velocity). since in this case gravity is not the only force acting on the object, we are not in a situation of free fall.

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