Answer:
1.97 seconds
Explanation:
t = Time taken
u = Initial velocity
v = Final velocity
s = Displacement
a = Acceleration due to gravity = 9.8 m/s²
![s=ut+\frac{1}{2}at^2\\\Rightarrow 21=4.5t+\frac{1}{2}\times -9.8\times t^2\\\Rightarrow 21=-4.5t-4.9t^2\\\Rightarrow 4.9t^2+4.5t-28=0\\\Rightarrow 49t^2+45t-280=0](https://tex.z-dn.net/?f=s%3Dut%2B%5Cfrac%7B1%7D%7B2%7Dat%5E2%5C%5C%5CRightarrow%2021%3D4.5t%2B%5Cfrac%7B1%7D%7B2%7D%5Ctimes%20-9.8%5Ctimes%20t%5E2%5C%5C%5CRightarrow%2021%3D-4.5t-4.9t%5E2%5C%5C%5CRightarrow%204.9t%5E2%2B4.5t-28%3D0%5C%5C%5CRightarrow%2049t%5E2%2B45t-280%3D0)
Solving the above equation we get
![t=\frac{-45+\sqrt{45^2-4\cdot \:49\left(-280\right)}}{2\cdot \:49}, \frac{-45-\sqrt{45^2-4\cdot \:49\left(-280\right)}}{2\cdot \:49}\\\Rightarrow t=1.97, -2.89](https://tex.z-dn.net/?f=t%3D%5Cfrac%7B-45%2B%5Csqrt%7B45%5E2-4%5Ccdot%20%5C%3A49%5Cleft%28-280%5Cright%29%7D%7D%7B2%5Ccdot%20%5C%3A49%7D%2C%20%5Cfrac%7B-45-%5Csqrt%7B45%5E2-4%5Ccdot%20%5C%3A49%5Cleft%28-280%5Cright%29%7D%7D%7B2%5Ccdot%20%5C%3A49%7D%5C%5C%5CRightarrow%20t%3D1.97%2C%20-2.89)
So, the time the package was in the air is 1.97 seconds
Answer:
160J
Explanation:
Given force = 8N and total distance = 20 meters
Workdone = force x distance
= 8 x 20
= 160J
Therefore, workdone by Riley in pulling the hoover is 160J
Explanation:
When m=<em>mass</em>
G=<em>a</em><em>c</em><em>c</em><em>e</em><em>l</em><em>e</em><em>r</em><em>a</em><em>t</em><em>i</em><em>o</em><em>n</em><em> </em><em>d</em><em>u</em><em>e</em><em> </em><em>t</em><em>o</em><em> </em><em>gravity</em>
<em> </em><em> </em><em> </em><em> </em><em> </em><em> </em><em> </em><em> </em><em> </em><em> </em><em> </em><em>H</em><em>=</em><em>h</em><em>e</em><em>i</em><em>g</em><em>h</em><em>t</em>
<em>U</em><em>s</em><em>i</em><em>n</em><em>g</em><em> </em><em>f</em><em>o</em><em>r</em><em>m</em><em>u</em><em>l</em><em>a</em>
<em>M</em><em>g</em><em>h</em>
<em>(</em><em>M</em><em>=</em><em>6</em><em>, </em><em>g</em><em>=</em><em>10</em><em>,</em><em>h</em><em>=</em><em>?</em><em>) </em>
6×10×h
=60joules
Answer:
the velocity is zero, the acceleration is directed downward, and the force of gravity acting on the ball is directed downward
Explanation:
Is this exercise in kinematics
v = v₀ - g t
where g is the acceleration of the ball, which is created by the attraction of the ball to the Earth.
At the highest point
velocity must be zero.
The acceleration depends on the Earth therefore it is constant at this point and with a downward direction.
The force of the earth on the ball is towards the center of the Earth, that is, down
all other alternatives are wrong