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3 years ago

How long would it take Exena to close the door if she doubled the magnitude of the force applied to the door

Physics

1 answer:

vova2212 [387]3 years ago

5 0

Answer:

y /y₀ = 1 /√2 = 0.70

Explanation:

To close the door, a torque must be applied in such a way that there is an angular acceleration and after a period of time the angle of the door moves.

If the force is doubled keeping the other parameters without altering angular acceleration is

F r = I α

α = F r / I

if we double the force

α = 2F r / I

α=2 α₀

let's use the angular kinematics relations

θ = w₀ t + ½ α t²

we assume the door was still before pushing it

θ = ½ a t²

t = √ (2θ / a)

as we saw the angular acceleration is double

t = √ (2θ / 2a₀)

t = 1 / √2 a₀

the relationship between the two times is

y /y₀ = 1 /√2 = 0.70

This time that has been reduced closes the door.

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a stomp rocket takes 1.5 seconds to reach its maximum height what was the initial velocity and what was the maximum height ?

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1) Vf = Vo - gt; Vf = 0 => Vo = gt = 9.8m/s^2 * 1.5s = 14.7 m/s

2) d = Vo*t - gt^2 /2 = 14.7m/s*1.5 - 9.8m/s^2 * (1.5s)^2 / 2 = 11.02 m

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3 years ago

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Two blocks joined by a string have masses of 6 and 9 kg. They rest on a frictionless horizontal surface. A 2nd string, attached

Tom [10]

Answer:

12N

Explanation:

Suppose the string mass is negligible, the total mass of the 2 block system is 6 + 9 = 15 kg

So the acceleration of the system when subjected to 30N force is

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So both blocks would have the same acceleration, however, the force acting on the 6kg block would have a magnitude of

f = am = 2 * 6 = 12N

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3 years ago

A ball thrown vertically upward is caught by the thrower after 2.93 s. Find the initial velocity of the ball. The acceleration o

almond37 [142]

Answer:

The initial velocity of the ball is 28.714 m/s

Explanation:

Given;

time of flight of the ball, t = 2.93 s

acceleration due to gravity, g = 9.8 m/s²

initial velocity of the ball, u = ?

The initial velocity of the ball is given by;

v = u + (-g)t

where;

v is the final speed of the ball at the given time, = 0

g is negative because of upward motion

0 = u -gt

u = gt

u = (9.8 x 2.93)

u = 28.714 m/s

Therefore, the initial velocity of the ball is 28.714 m/s

7 0

3 years ago

Cho hai điện tích q1=q2=8.10^-7 C đặt cách nhau 5cm. Xác định cường độ điện trường tại điểm:

Aleksandr [31]

Answer: b

Explanation:

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2 years ago

MamaMia's Pizza purchases its pizza delivery boxes from a printing supplier. MamaMia's delivers on-average 200 pizzas each month

Ira Lisetskai [31]

Answer:

a) 138 units

b) 17 units

c) 17 units

d) Total Cost = $353.35

Explanation:

Given:

Average pizzas delivered = 200

Charge of inventory holding = 30% of cost

Lead time = 7 days

Now,

a) Economic Order Quantity = $\sqrt\frac{2\times\textup{Annual Demand}\times\textup{Cost per Order}}{\textup{Carrying cost}}$

also,

Annual Demand = 200 × 12 = 2400

Cost per Order = Cost of Box + Processing Costs

= 30 cents + $10

= $10.30

and, Carrying Cost = $\frac{\textup{Total Inventory Cost}}{\textup{total annual demand}}$

= $\frac{\textup{Total Cost per order}\times\textup{Annual demand}\times\frac{25}{100}}{\textup{Annual demand}}$

= $\frac{\$10.30\times2400}\times\frac{25}{100}}{2400}$

= $2.575

Therefore,

Economic Order Quantity = $\sqrt\frac{2\times\textup{2400}\times\textup{10.30}}{\textup{2.575}}$

= 138.56 ≈ 138 units

b) Reorder Point

= (average daily unit sales × the lead time in days) + safety stock

= ( $\frac{200}{30}\times7$

= 46.67 ≈ 47 units

c) Number of orders per year = $\frac{\textup{Annual Demand}}{\textup{Economic order quantity}}$

= $\frac{\textup{2400}}{\textup{138}}$

= 17.39 ≈ 17 units

d) Total Annual Cost (Total Inventory Cost)

= Ordering Cost + Holding Cost

Now,

The ordering Cost = Cost per Order × Total Number of orders per year

= $10.30 × 17

= $175.1

and,

Holding Cost = Average Inventory Held × Carrying Cost per unit

Average Inventory Held = $\frac{\textup{0+138}}{\textup{2}}$ = 69

Carrying Cost per unit = $2.575

Holding Cost = 69 × $2.575 =

$177.675

Therefore,

Total Cost = Ordering Cost + carrying cost

= $175.1 + $177.675 = $353.35

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3 years ago

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