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Y_Kistochka [10]
3 years ago
13

While exploring a castle, Exena the Exterminator is spotted by a dragon who chases her down a hallway. Exena runs into a room an

d attempts to swing the heavy door shut before the dragon gets her. The door is initially perpendicular to the wall, so it must be turned through 90∘ to close. The door has a height of 3.00 m and a width of 1.40 m , and its weight is 790 N . You can ignore the friction at the hinges.If Exena applies a force of220 N at the edge of the door and perpendicular to it, how muchtime does it take her to close the door?
Physics
1 answer:
Bogdan [553]3 years ago
5 0

Answer:

the time needed for her to close the door is 1.36 s.

Explanation:

given information:

Force, F = 220 N

width, r = 1.40 m

weight, W = 790 N

height, h = 3.00 m

angle, θ = 90° = π/2

to find the times needed to close the door we can use the following equation

θ = ω₀t + 1/2 αt²

where

θ = angle

ω = angular velocity

α = angular acceleration

t = time

in this case, the angular velocity is zero. thus,

θ = 1/2 αt²

now, we can find the angular speed by using the torque formula

τ = I α

where

τ = torque

I = Inertia

we know that

τ = F r

and

I = 1/3 mr²

so,

τ = I α

F r = 1/3 mr² α

α = 3 F/mr

  = 3 F/(w/g)r

  = 3 (220)/(790/9.8) 1.4

  = 5.85 rad/s²

θ = 1/2 αt²

π/2 = 1/2 5.85 t²

t = 1.36 s

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While riding a chairlift, a 55-kilogram skier is raised a vertical distance of 370 meters. What is the total change in the skier
Lelechka [254]

The change in the skier's gravitational potential energy is 199430 J.

<h3> Gravitational potential energy:</h3>

This is the energy of a body due to its position in a gravitational field. The  S.I unit of gravitational potential energy is Joules (J)

The Change in the skier's gravitational potential energy can be calculated using the formula below.

Formula:

  • ΔP.E = mg(Δh)............... Equation 1

Where:

  • ΔP.E = Change in the skier's potential energy
  • m = mass of the skier
  • Δh = change in height to which it was raised
  • g = acceleration due to gravity.

From the question,

Given:

  • m = 55 kg
  • Δh = 370 m
  • g = 9.8 m/s²

Substitute these values into equation 1

  • ΔP.E = 55×370×9.8
  • ΔP.E = 199430 J.

Hence, The change in the skier's gravitational potential energy is 199430 J.

Learn more about potential energy here: brainly.com/question/1242059

3 0
2 years ago
When a loop of current-carrying wire turns continuously in a magnetic field, a _________ is created.
Brrunno [24]
A solenoid is created
4 0
3 years ago
A 4.6-kg block of ice originally at 263 K is placed in thermal contact with a 15.7-kg block of silver (cAg = 233 J/kg-K) which i
Viktor [21]

Answer:

temperature at  326.44 K system achieve equilibrium

Explanation:

given data

mass of block of ice = 4.6 kg

temperature = 263 K

thermal contact =  15.7-kg

specific heat of silver  cAg = 233 J/kg-K

initially temperature = 1052 K

to find out

what temperature will the system achieve equilibrium

solution

first we consider final temperature of the system  is T

we know that specific heat of water (C w) = 4186 J(kg K)

and

specific heat of ice ( C i )  = 2030 J/(kg K)

and

latent heat of fusion of ice ( Lf ) = 3.33 × 10^{5} J/kg

and we know that system is insulated

so  heat lost by silver = heat generated by ice    .................1

so we can say

mass of silver × specific heat of silver  × ( initial temp - final temp ) = mass of  ice × specific heat of ice  × ( ice temp ) + mass of  ice × latent heat of fusion of ice + mass of  ice × specific heat of water  × (final temperature )  

put here value we get

mass of silver × specific heat of silver  × ( initial temp - final temp ) = mass of  ice × specific heat of ice  × ( ice temp ) + mass of  ice × latent heat of fusion of ice + mass of  ice × specific heat of water  × (final temperature )

15.7  × 233 × ( 1052 - T ) = 4.6 × 2030 × 10 + 4.6 × 3.33 × 10^{5} + 4.6 × 4286 × ( T - 273 )

solve we get

T =  326.44 K

so temperature at  326.44 K system achieve equilibrium

7 0
3 years ago
standing side by side, you and a friend step off a bridge and fall for 1.6s to the water below. your friend goes first, and you
Andrew [12]

(a) The distance will be more than 2.0 meters.

In fact, you starts your fall after your friend has already fallen 2.0 meters. This means that your friend has already accelerated for a while, therefore his velocity will be greater than yours. But this statement will be actually true for the entire fall, since you has some delay, therefore when your friend will hit the water, the separation between you and him will be greater than the initial separation of 2.0 meters.


b) First of all we need to calculate the height of the bridge with respect to the water. We know that you take 1.6 s to fall down, therefore we can use the following equation:

S=\frac{1}{2}gt^2=\frac{1}{2}(9.81 m/s^2)(1.6s)^2=12.56 m

We know that your friend will take 1.6 s to falls down. Instead, you start your jump after he has already fallen 2.0 m, therefore after a time given by the equation:

S=\frac{1}{2}gt^2

Using S=2.0 m,

t=\sqrt{\frac{2S}{g}}=\sqrt{\frac{2(2.0 m)}{9.81 m/s^2}}=0.64 s

So we know that you start your fall 0.64 s after your friend. Therefore, now we can find how much did you fall between the moment you started your fall (0.64 s) and the moment your friend hits the water (1.6 s). Using

t=1.6 s-0.64 s=0.96 s

we find

S=\frac{1}{2}gt^2=\frac{1}{2}(9.81 m/s^2)(0.96 s)^2 =4.52 m

So, when your friend hits the water, you just covered 4.52 m, while he already covered 12.56 m. Therefore, the separation between you and your friend is more than 2 meters.

8 0
3 years ago
In which of the following materials is the velocity of light greatest?
just olya [345]
<span>The velocity of light is by far the greatest in air. There is nothing in air to stop or impede the movement of light in air. When light travels in air it will not stop unless running into clouds, smoke, smoke, droplets, or impurities. Any other substance is harder for light to travel through.</span>
8 0
3 years ago
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