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Artyom0805 [142]
2 years ago
5

Listed below are four activities. In which activity is friction useful?

Physics
1 answer:
Likurg_2 [28]2 years ago
4 0

Answer:

a. climbing up a cliff

Explanation:

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The spring of a toy car stores 10 J of potential energy. Only 8 J of energy changes to kinetic energy as the car moves. What hap
son4ous [18]

Answer:

It has been converted into thermal energy due to friction

Explanation:

According to the law of conservation of energy, energy cannot be created nor destroyed, but only transformed from one form into another.

Applied to this problem, it means that the total initial energy of the spring-toy system must be conserved.

Therefore:

- At the beginning, the total energy stored in the spring is 10 J

- After the toy is released, the total energy must still be 10 J.

In reality, we are told that the kinetic energy of the car is only 8 J. The other 2 J have not been destroyed, but they have been converted into thermal energy, due to the presence of frictional forces that act against the motion of the toy car.

3 0
3 years ago
Which of the following changes would make a heat engine less efficient
DIA [1.3K]
A heat engine would be less efficient due to many factors 
For instance, a heat engine is more efficient when it uses in cold weather because there is a greater temperature difference ( Carnot Efficient )
A heat engine could be less efficient because of friction
Hope it helps I am a beginner
8 0
3 years ago
How does the Earth's rotation affect our view of stars?
rodikova [14]

you only see the stars once every twenty for hours so you can have daylight so because of Earth's rotation you only see the stars for a certain amount of hours

Explanation:

the Earth makes a full rotation so that's why my answer is what it is

5 0
3 years ago
A sling is used to give a stone an initial velocity of 20 at an angle of 30 above the horizontal. The stone travels through the
Luba_88 [7]

Answer:

Option E is correct.

There must be a horizontal wind opposite the direction of the stone's motion, because ignoring air resistance when calculating the horizontal range would yield a value greater than 32 m.

Explanation:

Normally, ignoring air resistance, for projectile motion, the range (horizontal distance teavelled) of the motion is given as

R = (u² sin 2θ)/g

where

u = initial velocity of the projectile = 20 m/s

θ = angle above the horizontal at which the projectile was launched = 30°

g = acceleration due to gravity = 9.8 m/s²

R = (30² sin 60°) ÷ 9.8

R = 78.53 m

So, Normally, the stone should travel a horizontal distance of 78.53 m. So, travelling a horizontal distance of 32 m (less than half of what the range should be without air resistance) means that, the motion of the stone was impeded, hence, option E is correct.

There must be a horizontal wind opposite the direction of the stone's motion, because ignoring air resistance when calculating the horizontal range would yield a value greater than 32 m.

Hope this Helps!!!

7 0
3 years ago
A man pushes a crate along a factory floor by exerting a force of 55 N. If
nika2105 [10]

Answer:

it's 220 J

the second one

7 0
2 years ago
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