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Leya [2.2K]
3 years ago
14

A 450-N rightward force is used to drag a large box across the floor with a constant velocity of 1.2 m/s. The coefficient of fri

ction between the box and the floor is 0.795. Determine the mass of the box.
Physics
1 answer:
Nikolay [14]3 years ago
8 0

Answer:

the mass of the box is 51.98 kg.

Explanation:

Given;

applied horizontal force, F = 450 N

coefficient of friction, μ = 0.795

constant velocity, v = 1.2 m/s

At constant velocity, the acceleration of the object is zero and the net force will be zero.

F_{Net} = F - F_k\\\\0 = F - F_k\\\\F_k = F\\\\\mu \ N = F\\\\\mu (mg) = F\\\\m = \frac{F}{\mu  g} \\\\m = \frac{405}{0.795 \ \times \ 9.8} \\\\m = 51.98 \ kg

Therefore, the mass of the box is 51.98 kg.

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A cake is removed from a 375°F oven and placed on a cooling rack in a 63°F room. After 30 minutes the cake is 175°F. When will i
marysya [2.9K]

Answer:

The cake will be at temperature 150°F at after 37.34 minutes

Explanation:

Let T be the temperature of the cake at any time

T∞ be the temperature around the cooling rack = 63°F

T₀ be the initial temperature of the cake = 375°F

And m, c, h are all constants from the cooling law relation

From Newton's law of cooling

Rate of Heat loss by the cake = Rate of Heat gain by the environment

- mc (d/dt)(T - T∞) = h (T - T∞)

(d/dt) (T - T∞) = dT/dt (Because T∞ is a constant)

dT/dt = (-h/mc) (T - T∞)

Let (h/mc) be k

dT/(T - T∞) = -kdt

Integrating the left hand side from T₀ to T and the right hand side from 0 to t

In [(T - T∞)/(T₀ - T∞)] = -kt

(T - T∞)/(T₀ - T∞) = e⁻ᵏᵗ

(T - T∞) = (T₀ - T∞)e⁻ᵏᵗ

Inserting the known variables

(T - 63) = (375 - 63)e⁻ᵏᵗ

(T - 63) = 312 e⁻ᵏᵗ

At 30 minutes, T = 175°F

175 - 63 = 312 e⁻ᵏᵗ

112/312 = e⁻ᵏᵗ

- kt = In (112/312) = In (0.3590)

- 30k = - 1.025

k = 1.025/30 = 0.0342 /min

When the temp is 150°F,

(T - T∞) = (T₀ - T∞)e⁻ᵏᵗ

(150 - 63) = 312 e⁻ᵏᵗ

e⁻ᵏᵗ = (87/312) = 0.2788

- kt = In 0.2788 = - 1.277

t = 1.277/k = 1.277/0.0342 = 37.34 min.

7 0
4 years ago
A mover uses a ramp to load a crate of nails onto a truck. The crate, which must be lifted 1.5 m from the street to the bed of t
jonny [76]

Answer:

<h2>3</h2>

Explanation:

Using the efficiency formula. Efficiency = MA/VR * 100%

MA = Mechanical Advantage

VR = velocity ratio = \frac{distance\ moved\ by\ effort}{distance\ moved\ by\ load}

Distance moved by effort = 4.5m

distance moved by load = 1.5m

VR = 4.5/1.5 =3

Assuming efficiency is 100% (since friction can be ignored)

100% = MA/3 * 100%

1 = MA/3

MA = 3*1

MA = 3

Mechanical Advantage of the ramp is 3

8 0
4 years ago
A jar of tea is placed in sunlight until it reaches an equilibrium temperature of 31.8 ◦C . In an attempt to cool the liquid, wh
Shtirlitz [24]

Answer:

Explanation:

mass of liquid m₁ = 161 g

temperature t₁ = 31.8

final temperature t₂ = 28.8

Let m g of ice melted to cool the liquid

heat gained = mass x latent heat of fusion + mass x loss of temp x s heat of water

= m x 80 + m x 1 x ( 31.8 - 28.8 ) ( latent heat of ice = 80 cals/g )

= 83 m

heat lost  = 161 x 1 x ( 31.8 - 28.8 ) ( specific heat of water = 1 cal / g / k )

= 161 x 3

heat lost = heat gained

83 m = 161 x 3

m = 5.82 g

mass of remaining ice = 131 - 5.82

= 125.18 g

4 0
4 years ago
How much do you know about the water cycle and the impact that humans have on the water cycle?
Eddi Din [679]
The water cycle is the process when water circulates from the oceans on the Earth, the atmosphere, land, this also involves rainfall and snow, sewers in rivers and streams, and then it returns to the atmosphere by evaporation and transpiration. Humans impact the water cycle by irrigation, urbanization, deforestation, and storing water in reservoirs.
7 0
3 years ago
4. Calculate the total resistance for two 180 ohm resistors connected in<br> parallel
solmaris [256]

Answer:

90 ohms

Explanation:

1/r = 1/180 + 1/180

1/r= 2/180

take the reciprocal of 2/180 which is 180/2 and its 90 ohms

3 0
3 years ago
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