What are the 2 forces acting on a free falling body?

Question

What are the 2 forces acting on a free falling body? and
How can i solve for this :

Given :

at the ground : if a ball is thrown upward w/ a velocity of 45m/s . .what is the time it takes for it to reach 500m above the ground?

Please help me solve this

Answer 1

Two forces act on a body falling through the atmosphere, one is gravity and the other is air resistance, also known as drag.



With the data given, the ball will not reach the required distance. That is even without considering atmospheric resistance.

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Edit for Nishit(Below): You can use v=u+at, where t is the time required for the velocity to be zero. It has to be zero, since gravitational acceleration acts in the direction opposite that of the ball's initial motion. You can see that the ball stops going upwards after 4.6 seconds. Now use S = ut + ½gt² with u as 45 m/s, t as 4.6 seconds and g as -9.8 m/s². You can see that the ball will never reach 500 m. You cannot make assumptions that defy physics and put them into quadratic equations. Besides, your quadratic solution is wrong too.

Answer 2

Since they would soon syncronise their speed with that of the lift in effect they would stop falling as they would no longer perceive the sensation of falling to them it would just be the norm. If the lift was large enough and had food and water then they could live a full if somewhat lonely life The question is not so silly from a Physics point of view because in effect you are describing the existence of a human on earth as it moves forever through an expanding space So they would die of starvation since you are cruel and gave them air and no water / food, but it would not be from falling because they cease to fall when their velocity matches that of the body they are travelling in - this is why astronauts do not continue to perceive the force of accelaration or speed once they are not affected by the earths gravity as they are now essentially at the same state as the space craft Interesting question :)

Answer 3

Two forces acting on a free falling body :

1. Gravitational force acting downward, i.e. in the direction of hte body's motion, and

2. frictional force caused by the air around acting upward against the body's motion.



the problem:

use the formula:

v=u+at

where v=final velocity of the baal=0 m/s

u=45 m/s

a= -g= -10 metres/second squared



and find the time the baal takes to reach the highest point. then use the formula



h=ut+(1/2)a(t^2)



where h is the max. height that the ball gets to. you'll find it doesnt get to 500 metres at all...but it's max. height is 101.25 metres.



the value of g has ben approximated to 10..it's actually around 9.8 metres/second squared.

Answer 4

u(initial velocity)=45m/s

a(acceleration)= -9.8m/s^2

s(distance travelled)=500m

2nd equation of motion =>

s = ut + 1/2 at^2

500 = 45t - 4.9t^2

==> -4.9t^2 + 45t - 500 = 0 [Quadratic eqn.]

==> 4.9t^2 - 45t + 500 = 0

Using Quadratic formula,

(45 + 99) / 2 ==> t = 72s



The ball will take approximately 72s to reach a distance of 500m in the air.

Answer 5

in a free falling body, there are: gravity force, and friction between the body and the air.



S= Vo. t + 1/2 a. t(square)

distance : velocity (at start) . time + 1/2 (acceleration, in here gravity) . time(square)



500m = 45m/s . time + 1/2 . -10 m/s(square) . time(square)



500 = 45 t - 5 t(square)



-divided by 5-



100= 9t - t(square)



t(square) - 9 t - 100 = 0



(t - 10) (t + 1) = 0



so:

t1= 10

t2 = -1



time needed= 10 seconds

Answer 6

Inertia and gravity.



But I won't help with the question. Sounds like some kind of test or homework you're doing. No cheating! lol

Answer 7

well,

to figure out the time.

you have to divide the distance by the speed.

which in technical terms is

t=s/v

so

t=500/45

you do the math.

and the two forces are gravity and mass