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3 years ago

1) Which of the following explains why a bicycle uses a gear?

2 answers:

7 0

1. "The gear decreases effort force" is the one among the following choices given in the question that <span>explains why a bicycle uses a gear. The correct option among all the options is option "C".

2. A can opener is a compound machine. The correct option among all the options that are given in the question is the second option or option "B".</span>

Marta_Voda [28]3 years ago

4 0

Answer:

1) D. The gear decreases resistance force

2) B. A car opener

Explanation:

1): A bicycle uses a gear to decrease the resistance force as when the gears are shifted, the chain moves from a larger ring to a smaller one thus reducing the surface area of the ring as well as friction which results into a greater speed by applying same amount of effort.

2): As a compound machine is a combination of more than one simple machine. Out of all the options, a car opener is said to be a compound machine as it consist of a lever, screw, wedge and axle and wheel.

These are some of the simple machines which combines to make a complex machine ( car opener ).

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A photograph is taken by letting light fall on a light-sensitive medium, which then records the image onto that medium. True or

Jet001 [13]

Answer;

The above statement is true.

-A photograph is taken by letting light fall on a light-sensitive medium, which then records the image onto that medium.

Explanation;

-A photograph is created when light is allowed to fall on a light-sensitive medium. The pattern of light creates an image that is recorded by the photographic device. How light or dark a photograph is depends on how much light was allowed to fall on the light-sensitive medium.

-A camera is a light-tight box that contains a light-sensitive material or device and a way of letting in a desired amount of light at particular times to create an image on the light-sensitive material.

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2 years ago

Light travels 300,000,000m/sec, and one year has approximately 32,000,000 seconds. A light year is the distance light travels in

dem82 [27]

A) 3 x 10 ^ 8
b) 3 x 10 ^ 5
c) 3.2 x 10 ^ 7
d) 9.6 x 10 ^ 15 m
e) 9.6 x 10 ^ 17 cm

3 0

2 years ago

A spring is compressed 0.035 m inside a dart gun. (K=500 N/m). The spring has elastic energy. Calculate it.

NARA [144]

The elastic potential energy of the spring is 0.31 J

Explanation:

The elastic potential energy of a spring is given by

$E=\frac{1}{2}kx^2$

where

k is the spring constant

x is the compression/stretching of the spring

For the spring in this problem, we have:

k = 500 N/m (spring constant)

x = 0.035 m (compression)

Substituting, we find the elastic potential energy:

$E=\frac{1}{2}(500)(0.035)^2=0.31 J$

Learn more about potential energy:

brainly.com/question/1198647

brainly.com/question/10770261

#LearnwithBrainly

6 0

2 years ago

A roller coaster car may be approximated by a block of mass m. Thecar, which starts from rest, is released at a height h above t

elena55 [62]

Answer:

The first part can be solved via conservation of energy.

$mgh = mg2R + K\\K = mg(h-2R)$

For the second part,

the free body diagram of the car should be as follows:

- weight in the downwards direction

- normal force of the track to the car in the downwards direction

The total force should be equal to the centripetal force by Newton's Second Law.

$F = ma = \frac{mv^2}{R}\\mg + N = \frac{mv^2}{R}$

where $N = 0$ because we are looking for the case where the car loses contact.

$mg = \frac{mv^2}{R}\\v^2 = gR\\v = \sqrt{gR}$

Now we know the minimum velocity that the car should have. Using the energy conservation found in the first part, we can calculate the minimum height.

$mgh = mg2R + \frac{1}{2}mv^2\\mgh = mg2R + \frac{1}{2}m(gR)\\gh = g2R + \frac{1}{2}gR\\h = 2R + \frac{R}{2}\\h = \frac{5R}{2}$

Explanation:

The point that might confuse you in this question is the direction of the normal force at the top of the loop.

We usually use the normal force opposite to the weight. However, normal force is the force that the road exerts on us. Imagine that the car goes through the loop very very fast. Its tires will feel a great amount of normal force, if its velocity is quite high. By the same logic, if its velocity is too low, it might not feel a normal force at all, which means losing contact with the track.

7 0

2 years ago

A refrigerator is used to remove 84 kj/min of heat from a tank. If the electric power consumed by the refrigerator is 1. 2 kw, w

zvonat [6]

Answer:

84 kj/min = 1.4 kj/sec

Power Out / Power In = Heat Out / Heat In - Coefficient of Performance

1.4 kj/sec / 1.2 kj/sec = 1.17 = COP

3 0

2 years ago