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Valentin [98]
2 years ago
4

A 60-kg crate is lowered from a loading dock to the floor using a top passing over fixed support. The rope exerts a constant upw

ard force on the crate of 500 N.
A. Will the crate accelerate? Explain.
B. What are the magnitude and direction of the acceleration of the crate?
C. How long will it take for the crate to reach the floor of the height of the loading dock is 1.4m above the floor?
D. How fast is the crate traveling when it hits the floor?
Physics
1 answer:
EastWind [94]2 years ago
5 0

Explanation:

a) What is the weight of the crate?

W = m*g = 60 kg *9.81 m/s^2 = 588.6 N

Sum of the forces in the vertical direction on the box (up is +) = F - W = 500 N - 588.6 N = -88.6 N

Since the forces do not add up to 0, then there is a net force on the crate which will cause the crate to accelerate.

b) F = m*a ==> a = F/m

a = -88.6 N / 60 kg = -1.48 m/s^2 (- means down since above we declared up as +)

c) Assume it starts from rest, vi = 0 m/s

Equation of motion in the vertical direction

h = h0 + v0*t + 1/2*a*t^2

h0 = 1.4 m

h = 0 m

v0 = 0 m/s

a = -1.48 m/s^2

0 = 1.4 m + 0 - 1/2* 1.48 m/s^2 * t^2

1.4 m = 1/2 * 1.48 m/s^2 * t^2

t = 1.38 s

d) vf = vi + a*t

vi = 0 m/s

vf = a*t = -1.48 m/s^2 * 1.38 s = -2.04 m/s

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You and your friend throw balloons filled with water from the roof of a several story apartment house. You simply drop a balloon
Aleks [24]

Answer:

Height = 53.361 m

Explanation:

There are two balloons being thrown down, one with initial speed (u1) = 0 and the other with initial speed (u2) = 43.12

From the given information we make the following summary

u_{1} = 0m/s

t_{1} = t

u_{2} = 43.12m/s

t_{2} = (t-2.2)s

The distance by the first balloon is

D = u_{1} t_{1}  + \frac{1}{2} at_{1}^2

where

a = 9.8m/s2

Inputting the values

D = (0)t + \frac{1}{2} (9.8)t^2\\ D = 4.9t^2

The distance traveled by the second balloon

D = u_{2} t_{2}  + \frac{1}{2} at_{2}^2

Inputting the values

D = (43.12)(t-2.2)  + \frac{1}{2} (9.8)(t-2.2)^2

simplifying

D = 4.9t^2 + 21.56t -71.148

Substituting D of the first balloon into the D of the second balloon and solving

4.9t^2 = 4.9t^2 + 21.56t -71.148 \\ 21.56t = 71.148\\ t = 3.3s

Now we know the value of t. We input this into the equation of the first balloon the to get height of the apartment

D = 4.9(3.3)^2\\ D = 53.361 m

7 0
2 years ago
You are sitting in your car at rest at a traffic light with a bicyclist at rest next to you in the adjoining bicycle lane. As so
grigory [225]

Answer:

Explanation:

Time duration during which acceleration exists in  bicycle =

23 / 12 = 1.91 s

Time duration during which acceleration exists in car

= 47 / 8 = 5.875 s

Distance covered by bicycle during acceleration ( t = 1.91 s )

= 1/2 x 12 x (1.91)²

= 21.88 mi

Distance covered by car during this time ( t = 1.91 s )

= 1/2 x 8 x (1.91)²

7.64 mi ,

velocity of car after 1.91 s

= 8 x 1.91 = 15.28 mi/h

Let after time 1.91 , time taken by them to meet each other be t

Total distance covered by cycle = total distance covered by car

21.88 + 23 t = 7.64 + 15.28t + 4 t²

21.88 = 7.64 - 7.72t +4 t²

4 t² -7.72 t -14.24 = 0

t = 2.83 s

Total time taken

= 2.83 + 1.91

= 4.74 s

So after 4.74 s they will meet each other.

b ) Maximum distance occurs when velocity of both of them becomes equal .

Velocity after 1.91 s of bicycle

12 x 1.91 = 23 mi/h

Velocity after 1.91 s of car

8 x 1.91 = 15.28 mi/h . Let after time t , the velocity of car becomes 23

15.28 + 8t = 23

t = .965 s

So after time .965 s , car has velocity equal to that of bicycle.

The bicycle will travel a distance of

= 21.88 + .965 x 23 = 44.075 mi

car will travel a distance of

7.64 + 15.28 x .965 + .5 x 8 x .965²

= 7.64 + 14.75 + 3.72

= 26.11 mi

Distance between car and bicycle

= 44.075 - 26.11 = 17.965 mi

= 17.965 x 1760

= 31618.4 ft.

5 0
2 years ago
A small light cylinder and a large heavy cylinder are released at the same time and roll down a ramp without slipping. Which one
forsale [732]

Answer:

C. Both reach the bottom at the same time.

Explanation:

For a rolling object down an inclined plane , the acceleration is given below

a = g sinθ / (1 + k² / r² )

θ is angle of inclination , k is radius of gyration , r is radius of the cylinder

For cylindrical object

k² / r² = 1/2

acceleration =  g sinθ  /( 1 + 1/2 )

= 2 g sinθ / 3  

Since it does not depend upon either mass or radius , acceleration of both the cylinder will be equal . Hence they will reach the bottom simultaneously.

6 0
2 years ago
There are many ways to lose weight, but a sustainable plan generally involves behavior modification related to diet and exercise
Anna007 [38]

The answer is adequate nutrition, regular physical activity, and practical ways to reduce calories while retaining important nutrients.

Explanation:

Despite that adequate nutrition, regular physical activity, and practical ways to reduce calories while retaining important nutrients is one of the best strategy to reducing weight, most time it is very difficult for those that want to reduce or control their weight to discipline themselves enough to follow these routine. But one an individual that want to loose weight or live a healthy lifestyle is able to follow these procedures he/she will surely loose weight.

5 0
2 years ago
A 25cm×25cm horizontal metal electrode is uniformly charged to +50 nC . What is the electric field strength 2.0 mm above the cen
saw5 [17]

Answer:

The electric field strength is 4.5\times 10^{4} N/C

Solution:

As per the question:

Area of the electrode, A_{e} = 25\times 25\times 10^{- 4} m^{2} = 0.0625 m^{2}

Charge, q = 50 nC = 50\times 10^{- 9} C[/etx]Distance, x = 2 mm = [tex]2\times 10^{- 3} m

Now,

To calculate the electric field strength, we first calculate the surface charge density which is given by:

\sigma = \frac{q}{A_{e}} = \frac{50\times 10^{- 9}}{0.0625} = 8\times 10^{- 7}C/m^{2}

Now, the electric field strength of the electrode is:

\vec{E} = \frac{\sigma}{2\epsilon_{o}}

where

\epsilon_{o} = 8.85\times 10^{- 12} F/m

\vec{E} = \frac{8\times 10^{- 7}}{2\times 8.85\times 10^{- 12}}

\vec{E} = 4.5\times 10^{4} N/C

7 0
2 years ago
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