Physics, 22.06.2019 06:30 mehokkj

Alead ball is dropped into a lake from a diving board 5m above the water . it hits the water with a certain velocity and then sink with constant velocity in bottom . it reaches the bottom 5 second after it is dropped if g= 10m/s2 . find depth of the lake and average velocity of the ball ?

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Answer from: steviekeen3

1. Depth of the lake: 50 m

Explanation:

The first part of the problem can be solved by using conservation of energy.

When it is dropped, all the mechanical energy of the ball is potential energy, given by:

U=mgh

where m is the mass, g is the gravitational acceleration and h is the height.

When the bal hits the water, all the mechanical energy has been converted into kinetic energy:

$K=\frac{1}{2}mv^2$

where m is the mass and v is the speed. Equalizing the two terms, we have:

$mgh=\frac{1}{2}mv^2\\2gh=v^2\\v=\sqrt{2gh}=\sqrt{2(10 m/s^2)(5 m)}=10 m/s$

Then the ball travels in the water, keeping this constant velocity, for t=5 s. So, the total distance traveled underwater (which is the depth of the lake) is

d=vt=(10 m/s)(5 s)=50 m

2. Average velocity: 9.2 m/s

Explanation:

The average velocity during the whole path of the ball is equal to the ratio between the total distance traveled and the total time taken:

$v=\frac{d}{t}$

We already know the total distance: 5 meters above the water and 50 m underwater, so

d = 5 m + 50 m = 55 m

For the total time, we need to calculate the time spent above the water, which is given by

$S=\frac{1}{2}gt_a^2\\t_a = \sqrt{\frac{2S}{g}}=\sqrt{\frac{2(5 m)}{10 m/s^2}}=1 s$

So the total time is: 1 second above the water + 5 seconds underwater:

t = 1 s + 5 s = 6 s

Therefore, the average velocity is

$v=\frac{55 m}{6 s}=9.2 m/s$

Answer from: Quest

luster is not a good characteristic to use by itself because luster is the property of minerals that indicates how much the surface of a mineral reflects light. the luster of a mineral is affected by the brilliance of the light used to observe the mineral surface.

Answer from: Quest

distance on the y-axis and time on the x-axis.

explanation:

the instantaneous velocity = change in position/time taken

the slope of the graph should give instantaneous velocity.

slope of a graph = change in value of y -axis / change in values of x -axis

comparing both the equations

change in value of y -axis = change in position

change in values of x -axis = time taken

so position values should be on the y axis and time values should be on the x axis.

distance on the y-axis and time on the x-axis.

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Alead ball is dropped into a lake from a diving board 5m above the water . it hits the water with a...