⭐ 𝑬𝒍𝒆𝒄𝒕𝒓𝒊𝒄 𝒄𝒂𝒓 𝑫𝒖𝒃𝒊𝒏𝒂 𝑬𝒗𝒐 ⭐

Task 30.2

A 60 W LED lamp emits a luminous flux of 7200 lm. Determine the luminous efficiency of the lamp.

ɳ = φ /P

ɳ - luminous efficiency, lm/W

φ - luminous flux, lm

P - power, W

ɳ = 7200/60 = 120 lm/W

Task 30.3

Calculate the energy consumed by a 60 W lamp in 90 minutes.

E = P · t

E – energy, W · h

P – power, W

t – time, h

E = 60 · 1.5 = 90 W · h

Task 30.4

What is the total luminous flux emitted by a headlight if the luminous intensity is 50 cd?

Φ = 4 · π · I

Φ = 4 · 3.14 · 50 = 628 lm.

Task 31.1

In an isosceles trapezoid, the sides are 1 m, the bases are 1 m and 1.5 m. Calculate the area of ​​the trapezoid.

S = ((a + b)/2) · (c^2 – ¼ · (b-a)^2)^0.5

S = ((1 + 1.5)/2) · (1^2 – ¼ · (1.5-1)^2)^0.5 = 1.25 · 0.968 = 1.21 m^2

Task 31.2

The hood of a car is made of carbon fiber with a density of 1500 kg/m^3. Calculate the mass of the hood if its thickness is 4 mm and its surface area is 1.2 m^2

m = p · V

V = S · t

V = 1.2 · 0.004 = 0.0048 m^3

m = 1500 · 0.0048 = 7.2 kg

Task 32.1

The trunk door is a rectangle with sides of 1.4 m and 1.8 m. What volume of paint is required to paint the door side if the paint consumption is 0.25 l/m^2?

V = S · R

S = a · b

S = 1,8 · 1,4 = 2,52 m^2

V = S · R = 2,52 · 0,25 = 0,756 l

Task 32.2

The trunk door is made of carbon fiber with a density of 1500 kg/m^3. Calculate the mass of the door if its thickness is 4 mm and the surface area is 2.5 m^2

m = p · V

V = S · t

V = 2.5 · 0.004 = 0.01 m^3

m = 1500 · 0.01 = 15 kg

Task 32.3

In an isosceles triangle ABC, a height BD is drawn. The lateral sides of the triangle AB, AC are equal to 1.8 m. What is the height BD if the angle ∠A = 40°?

BD = AB · sin ∠A

BD = 1,8 · sin ∠40° = 1,8 · 0,643 ≈ 1,157 m

Task 33.1

The area of ​​the working surface of the spoiler is 0.6 m^2. The angle of attack is 40°. The lift coefficient is Cl = 1.1. Calculate the downforce of the spoiler at a speed of 200 km/h.

F = Cl · (p · υ^2)/2 · S

F - downforce, N;

p - air density, kg/m^3;

F = 1.1 · (1.2 · 55.56^2)/2 · 0.6 = 1.1 · 1852 · 0.6 = 1224 N

Task 34.1

Determine the angle by which the beam reflected from a flat mirror will rotate if the mirror is rotated by 20°

α = 2 · β

α = 40°

Task 35.1

A car weighing 1200 kg is parked on a road with a slope of 5°. The coefficient of friction of the wheels is 0.8. Determine the friction force.

F = µ · N

N = m · g · cos(α)

F – friction force, N

µ - coefficient of friction

N – normal reaction force, N

m – car mass, kg

g – acceleration of gravity, m/s^2

α – road slope angle, °

N = 1200 · 9.81 · cos 5° = 11735 N

F = 0.8 · 11735 = 9388 N

Task 35.2

At what speed does a car travel if its wheels with a diameter of 635 mm rotate at a frequency of 1000 rpm

V = L · ω

L = π · d

L = 3,14 · 635 = 1999 mm ≈ 2 m

V = 2 · 1000 · 60 / 1000 = 120 km/h

Task 36.1

The nut presses the wheel disk with a force of 12 kN. What pressure does the nut exert on the disk if the contact area of ​​the nut is S = 0.01 m^2

P = F/S

P = 12000/0.01 = 1.2 MPa

Task 37.1

What is the charging power if the voltage in the network is 220 V and the current is 10 A?

P = U · I

P = 220 · 10 = 2.2 kW