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kozerog [31]
3 years ago
11

A refrigerator has a power of 90 w and is left on for 24 hours. A hair dryer has a power of 900 w an is on for 20 minutes. Which

statement correctly compares the energy used by these devices
Physics
1 answer:
Musya8 [376]3 years ago
4 0

The refrigerator has consumed more energy

Explanation:

The relationship between power and energy consumed by a device is given by

E=Pt

where

E is the energy

P is the power

t is the time elapsed

For the refrigerator, we have

P = 90 W

t = 24 h \cdot 3600 = 86400 s

Therefore the energy consumed is

E=(90)(86400)=7.78\cdot 10^6 J

For the hair dryer, we have

P = 900 W

t = 20 min \cdot 60 = 1200 s

Therefore the energy consumed is

E=(900)(1200)=1.08\cdot 10^6 J

Therefore, the refrigerator has consumed more energy.

Learn more about power:

brainly.com/question/7956557

#LearnwithBrainly

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If the sprinter from the previous problem accelerates at that rate for 20 m, and then maintains that velocity for the remainder
kakasveta [241]

Question:

A 63.0 kg sprinter starts a race with an acceleration of 4.20m/s square. What is the net external force on him? If the sprinter from the previous problem accelerates at that rate for 20m, and then maintains that velocity for the remainder for the 100-m dash, what will be his time for the race?

Answer:

Time for the race will be t = 9.26 s

Explanation:

Given data:

As the sprinter starts the race so initial velocity = v₁ = 0

Distance = s₁ = 20 m

Acceleration = a = 4.20 ms⁻²

Distance = s₂ = 100 m

We first need to find the final velocity (v₂) of sprinter at the end of the first 20 meters.

Using 3rd equation of motion

(v₂)² - (v₁)² = 2as₁ = 2(4.2)(20)

v₂ = 12.96 ms⁻¹

Time for 20 m distance = t₁ = (v₂ - v ₁)/a

t₁ = 12.96/4.2 = 3.09 s

He ran the rest of the race at this velocity (12.96 m/s). Since has had already covered 20 meters, he has to cover 80 meters more to complete the 100 meter dash. So the time required to cover the 80 meters will be

Time for 100 m distance = t₂ = s₂/v₂

t₂ = 80/12.96 = 6.17 s

Total time = T = t₁ + t₂ = 3.09 + 6.17 = 9.26 s

T = 9.26 s

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3 years ago
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