Air at 20ºc with a convection heat transfer coefficient of 25 w/m2·k blows over a horizontal steel hot plate (k = 43 w/m·k). the
1 answer:
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(a) 18.9 m/s
The motion of the stone consists of two independent motions:
- A horizontal motion at constant speed
- A vertical motion with constant acceleration () downward
We can calculate the components of the initial velocity of the stone as it is launched from the ground:
The horizontal velocity remains constant, while the vertical velocity changes due to the acceleration along the vertical direction.
When the stone reaches the top of its parabolic path, the vertical velocity has became zero (because it is changing direction): so the speed of the stone is simply equal to the horizontal velocity, therefore
(b) 22.2 m/s
We can solve this part by analyzing the vertical motion only first. In fact, the vertical velocity at any height h during the motion is given by
(1)
where
is the initial vertical velocity
is the vertical velocity at height h
is the acceleration due to gravity (negative because it is downward)
At the top of the parabolic path, , so we can use the equation to find the maximum height
So, at half of the maximum height,
And so we can use again eq(1) to find the vertical velocity at h = 6.9 m:
And so, the speed of the stone at half of the maximum height is
(c) 17.4% faster
We said that the speed at the top of the trajectory (part a) is
while the speed at half of the maximum height (part b) is
So the difference is
And so, in percentage,
So, the stone in part (b) is moving 17.4% faster than in part (a).
I'm not quite sure what happens to Fay so I didn't finish but hope it helps
Answer:
Explanation:
<u>Free Fall Motion</u>
A free-falling object refers to an object that is falling under the sole influence of gravity. If the object is dropped from a certain height h, it moves downwards until it reaches ground level.
The speed vf of the object when a time t has passed is given by:
Where
Similarly, the distance y the object has traveled is calculated as follows:
If we know the height h from which the object was dropped, we can solve the above equation for t:
The stadium is h=32 m high. A pair of glasses is dropped from the top and reaches the ground at a time:
The pen is dropped 2 seconds after the glasses. When the glasses hit the ground, the pen has been falling for:
Therefore, it has traveled down a distance:
Thus, the height of the pen is: