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3 years ago

If a block of wood dropped from a tall building has attained a velocity of 78.4 m/s how long has it been falling

Physics

1 answer:

ryzh [129]3 years ago

5 0

Gravity adds 9.8 m/s to the speed of a falling object every second.

An object dropped from 'rest' (v = 0) reaches the speed of 78.4 m/s after falling for (78.4 / 9.8) = <em>8.0 seconds</em> .

In order to test this, you'd have to drop the object from a really high cell- tower, building, or helicopter. After falling for 8 seconds and reaching a speed of 78.4 m/s, it has fallen 313.6 meters (1,029 feet) straight down.

The flat roof of the Aon Center . . . the 3rd highest building in Chicago, where I used to work when it was the Amoco Corporation Building . . . is 1,076 feet above the street.

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Given 1 inch ≡ 2.54 cm and 1 foot ≡

d1i1m1o1n [39]

Answer:

2991.47 [cm^2]

Explanation:

To solve this problem we must perform a dimensional analysis and use the corresponding conversion values:

$3.22[ft^{2}]*\frac{12^{2}in^{2} }{1^{2}ft^{2}} *\frac{2.54^{2}cm^{2} }{1^{2}in^{2} } \\2991.47[cm^{2}]$

3 0

3 years ago

Plz help, and show work

pentagon [3]

Answer:

1. 2.67 s

2. 0.1 m/s²

Explanation:

1. Determination of the time taken for the penguin to fall.

Height (h) of cliff = 35 m

Acceleration due to gravity (g) = 9.8 m/s²

Time (t) =?

h = ½gt²

35 = ½ × 9.8 × t²

35 = 4.9 × t²

Divide both side by 4.9

t² = 35 / 4.9

Take the square root of both side

t = √(35 / 4.9)

t = 2.67 s

Thus, it will take 2.67 s for the penguin to fall onto the head of a napping polar bear.

2. Determination of the acceleration of the penguin.

Initial velocity (u) = 0 m/s.

Final velocity (v) = 2 m/s.

Time (t) = 20 s

Acceleration (a) =?

a = (v – u)/t

a = (2 – 0)/ 20

a = 2 / 20

a = 0.1 m/s²

Thus, the acceleration of the penguin is 0.1 m/s²

8 0

2 years ago

In a pickup game of dorm shuffleboard, students crazed by final exams use a broom to propel a calculus book along the dorm hallw

RSB [31]

Answer:

The coefficient of kinetic is

$u_{k}=0.59$

Explanation:

The forces in the axis 'x' and 'y' using law of Newton to find coefficient of kinetic friction

ΣF=m*a

ΣFy=W-N=0

ΣFy=Fn-Fu=m*a

$F_{u} =u_{k} *N\\F_{N}=25N\\N=W\\N=3.5kg*9.8\frac{m}{s^{2} }=34.3N$

$F_{N}-F_{u}=m*a\\F_{N}-u_{k}*N=m*a\\u_{k}*N=F_{N}-m*a\\u_{k}=\frac{F_{N}-m*a}{N}$

Now to find the coefficient can find the acceleration using equation of uniform motion accelerated

$v_{f} ^{2}=v_{o}^{2}+2*a(x_{f}-x_{o})\\x_{o}=0\\v_{o}=0\\v_{f} ^{2}=2*a*x_{f}\\a=\frac{v_{f} ^{2}}{2*a*x_{f}}\\ a=\frac{(1.53\frac{m}{s} )^{2}}{2*0.91m}\\a= 1.28 \frac{m}{s^{2} }$

So replacing the acceleration can fin the coefficient:

$u_{k}=\frac{F_{N}-m*a }{N}\\u_{k}=\frac{25N-(3.5kg*1.28\frac{m}{s^{2}} }{34.3N} \\u_{k}=0.59$

5 0

3 years ago

What is the speed of sound for a noise that travels 2km in 5.8s?

Gnesinka [82]

Answer:

Explanation:

Speed is defined as the rate at which an object covers a particular distance. So the formula for determining speed is given as the ratio of distance to time taken for covering that distance.

Speed = Distance/Time

As here the distance is given in km units and time in s units, so the units of any one parameter should be changed. Since we know that speed of sound is always about 300 m/s. So it is better to convert the unit of distance from km to m.

Hence, now the distance traveled by the noise is 2000 m and time taken is 5.8 s.

So the speed of noise = Distance/Time = 2000/5.8=345 m/s.

Thus, the speed of noise is slightly greater than the speed of sound and it is found to be 345 m/s.

5 0

3 years ago

It's not important to monitor your heart rate during moderate intensity activities. True False

Mama L [17]

I think it is False

hope this helps :3

5 0

3 years ago

Read 2 more answers