All categories

3 years ago

A train travels 57 kilometers in 3 hours, and then 87 kilometers in 2 hours. What is its average speed? km/hr

1 answer:

3 0

Average speed (v) = total distance(d) / total time (t)
d = 57 + 87km = 144km
t = 2 + 3hrs = 5hrs
v = d÷t = 144÷5 = 28.8km/hr

You might be interested in

Two point charges, initially 3 cm apart, are moved to a distance of 1 cm apart. By what factor does the resulting electric force

Solnce55 [7]

The answer is B (1/9).

6 0

3 years ago

Excellent human jumpers can leap straight up to a height of

Firlakuza [10]

For a human jumper to reach a height of 110 cm, the person will need to leave the ground at a speed of 4.65 m/s.

We can calculate the initial speed to reach 110 cm of height with the following equation:

$v_{f}^{2} = v_{i}^{2} - 2gh$

Where:

$v_{f}$ : is the final speed = 0 (at the maximum height of 110 cm)

$v_{i}$ : is the initial speed =?

g: is the acceleration due to gravity = 9.81 m/s²

h: is the height = 110 cm = 1.10 m

Hence, the <u>initial velocity</u> is:

$v_{i} = \sqrt{v_{f}^{2} + 2gh} = \sqrt{2*9.81 m/s^{2}*1.10 m} = 4.65 m/s$

Therefore, the initial speed that the person must have to reach 110 cm is 4.65 m/s.

You can see another example here: brainly.com/question/13359681?referrer=searchResults

I hope it helps you!

4 0

2 years ago

A boat takes 3.0 hours to travel 50 km down a river, then 5.4 hours to return. Determine the speed of the water in the river.

Nutka1998 [239]

Answer:

3.7 km/h

Explanation:

Let's call v the proper speed of the boat and v' the speed of the water in the river.

When the boat travels in the direction of the current, the speed of the boat is:

v + v'

And it covers 50 km in 3 h, so we can write

$v+v' = \frac{50 km}{3 h}=16.7 km/h$ (1)

When the boat travels in the opposite direction, the speed of the boat is

v - v'

And it covers 50 km in 5.4 h, so

$v-v'=\frac{50 km}{5.4 h}=9.3 km/h$ (2)

So we have a system of two equations: by solving them simultaneously, we find the value of v and v':

$v+v'=16.7 \\v-v'=9.3$

Subtracting the second equation from the first one we get:

$(v+v')-(v-v')=16.7-9.3\\2v'=7.4\\v'=3.7$

So, the speed of the water is 3.7 km/h.

5 0

3 years ago

Gravitational potential energy is a form of potential energy

Gre4nikov [31]

True because it has "falling" ability

5 0

3 years ago

Which scale has 100 divisions from when the temperature when water freezes to the temperature when water boils

Westkost [7]

The Celsius scale ( $^{\circ} C$ ).

In the Celsius temperature scale, the temperature at which water freezes is set conventionally at $0^{\circ}C$ , while the temperature at which the water boils is set at $100^{\circ}C$ . The Celsius degree is then defined as the unit corresponding to 1/100 of this time interval, between the temperature of freezing and boiling of the water.

8 0

3 years ago