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julia-pushkina [17]
3 years ago
11

A ball is thrown horizontally from the top of a building 0.10 km high. The ball strikes the ground at a point 65 m horizontally

away from and below the point of release. What is the speed of the ball just before it strikes the ground?
Physics
2 answers:
stepladder [879]3 years ago
6 0

Answer:  well the time it takes to fall 100m is the same time it takes to travel 65m horizontally.  

The time to fall vertically, t is sqrt(2d/g). [this comes from d = 1/2at^2]  

so t = sqrt(2*100/9.8) = 4.52s.  

The vertical speed at that time is g*t = 9.8*4.52 = 44.3m/s  

The horizontal speed is the horizontal distance over the same 4.52s, = 65/4.52 = 14.4m/s.  

so the final velocity is = sqrt(44.3^2 + 14.4^2) = 46.6m/s

Explanation: yes

zalisa [80]3 years ago
3 0

Answer:

v = 46.55 m/s

Explanation:

It is given that,

A ball is thrown horizontally from the top of a building 0.10 km high, d = 0.1 km = 100 m

The ball strikes the ground at a point 65 m horizontally away from and below the point of release, h = 65 m

At maximum height, velocity of the ball is 0. So, using the equation of motion as :

d=ut+\dfrac{1}{2}at^2

Here, a = g

100=0+\dfrac{1}{2}\times 9.8t^2

t=4.51\ s

Let v_x is the horizontal velocity of the ball. It is calculated as :

v_x=\dfrac{65\ m}{4.51\ s}=14.41\ m/s

Let v_y is the final speed of the ball in y direction. It can be calculated as :

v_y^2+u_y^2=2as

u_y=0

v_y^2=2gd

v_y^2=2\times 9.8\times 100

v_y=44.27\ m/s

Let v is the speed of the ball just before it strikes the ground. It is given by :

v=\sqrt{v_x^2+v_y^2}

v=\sqrt{14.41^2+44.27^2}

v = 46.55 m/s

So, the speed of the ball just before it strikes the ground is 46.55 m/s. Hence, this is the required solution.

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Answer:

<u>Assuming b = 9.3i + 9.5j</u> <em>(b = 931 + 9.5 is wrong):</em>

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Explanation:

<u>Assuming b = 9.3i + 9.5j</u> <em>(b = 931 + 9.5 is wrong)</em> we can proceed as follows:  

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(a + b)\cdot b = [(8.6 + 9.3)i + (5.1 + 9.5)j]\cdot (9.3i + 9.5j) = (17.9i + 14.6j)\cdot (9.3i + 9.5j) = 305.17

d) The component of a along the direction of b is:

a*cos(\theta) = \frac{a\cdot b}{|b|} = \frac{128.43}{\sqrt{9.3^{2} + 9.5^{2}}} = 9.66

I hope it helps you!                        

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