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Lady bird [3.3K]
3 years ago
7

Simon is riding a bike at 12 km/h away from his friend Keesha.He throws a ball at 5 km/h back to Keesha, who is standing still o

n a sidewalk.
 
How fast would Keesha say the ball is traveling toward her?
Physics
1 answer:
Tems11 [23]3 years ago
5 0

I notice that even though we're working with frames of reference
here, you never said which frame the '5 km/hr' is measured in.

In fact !  You didn't even say which frame the '12 km/hr' of his
bike is measured in.

So there are several different ways this could go.  I'll do it the way
I THINK you meant it, but that doesn't guarantee anything.

-- Simon is riding his bike at 12 km/hr relative to the sidewalk,
away from Keesha.

-- He throws a ball at Keesha, at 5 km/hr relative to his own face.

-- Keesha sees the ball approaching her at (12 - 5) = 7 km/hr
relative to the ground and to her.

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The area of a triangle is 30 m². Using the equation A=12bh A = 1 2 b h , where b is base and h is height, solve for h if b = 3 m
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20 metres

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Se tienen 500g de alcohol etílico a una temperatura de -40 °C ¿Cuánto calor se necesita para transformarlo a vapor a una tempera
Feliz [49]

The question is: You have 500g of ethyl alcohol at a temperature of -40 ° C. How much heat is needed to transform it into steam at a temperature of 150ºC?

Answer: 233700 J heat is needed to transform ethyl alcohol into steam at a temperature of -40^{o}C to 150^{o}C.

Explanation:

Given: Mass = 500 g

Initial temperature = -40^{o}C

Final temperature = 150^{o}C

The standard value of specific heat of ethyl alcohol is 2.46 J/g ^{o}C.

Formula used to calculate the heat energy is as follows.

q = m \times C \times (T_{2} - T_{1})

where,

q = heat energy

m = mass of substance

C = specific heat

T_{1} = initial temperature

T_{2} = final temperature

Substitute the values into above formula as follows.

q = m \times C \times (T_{2} - T_{1})\\= 500 g \times 2.46 J/g^{o}C \times [150 - (-40)]^{o}C\\= 233700 J

Thus, we can conclude that 233700 J heat is needed to transform ethyl alcohol into steam at a temperature of -40^{o}C to 150^{o}C.

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