physics homework help.?

Question

okay, i totally SUCK at physics. so;

2. a 1.0-kilogram ball is dropped from the roof of a build 40. meters tall. what is the approx. time of fall? [neglect air resistance]

can you tell me what equation to use and what the given is? thanks.

Answer 1

u can use s=ut+1/2gt^2
in ur ques mass is given which is not needed,s=40,u=0(initial speed is 0)
therefore 40=1/2*9.8t^2
40=5(approx)*t^2
t=(8)^1/2

Answer 2

I like to use Xf = Xi + vi*t +1/2 *a*t^2 because I can get all other formulas from it.
Xf = final distance , 0 meters because its on the ground
Xi= initial distance, where does it start 40m.

vi = initial velocity which is zero because it is dropped, not thrown.
a = g (gravity) = 9.8 m/sec^2

The mass of the ball does not matter since without air resistance everything falls at the same acceleration of gravity.
The given is the height and the acceleration. They throw in the mass to throw you off.

So since the initial velocity is zero the equation shrinks to a more simpler equation. I think you can there there easily from here.

Answer 3

The mass is irrelevant. It is a red herring to throw you off. All bodies fall to the earth wit the acceleration of 9.81 meters/ second.
The equation to use for finding the time to fall 40 meters is the following;

distance = 1/2 acceleration *(time)^2

40 meters = 1/2 (9.81m/s/s)*(time)^2

Solve for time algebraically.

Answer 4

Let T be the time taken by the ball to reach the ground
Mass m = 1 kg
Distance d = 40 m

The ball when falling down falls with an acceleration which is equal to the gravitational accleration

Acceleration due to gravity = Distance / (Time)^2
9.8 = 40/T^2
T = Square root (40/9.8) = 2.02 sec

Answer 5

u will use equations of motion:

1. s=ut+1/2at^2
now u =0 ( since ball was initially at rest)

s=40m mass is not relevant ( since air resistance is not to be taken into account)

a = g =9.8 m/s^2

now u can calculate time

Answer 6

0.5 a t*t=40 t*t =8 t=3

Answer 7

the equation for free falling object is:
X=1/2at^2+vt+xi

X= final position
a=acceleration
t=time
v= initial velocity
xi= initial position

Mass has no effect on free falling object

Since the ball is dropped, it initial velocity is 0m/s and its final position is 0m

0m=1/2(-9.8m/s^2)t^2+40m
-40m= 1/2(-9.8m/s^2)t^2
-80m= (-9.8m/s^2)t^2
t^2= (80/9.8)
t= 2.86s

Answer 8

oye chinito as tu propia tarea o pregunatal a tu papa!!!!
buena suerte!!!!=]