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4 years ago

A train travels 94 kilometers in 3 hours, and then 65 kilometers in 3 hours. What is its average speed?

Physics

2 answers:

Norma-Jean [14]4 years ago

8 0

The average speed of the train is about 26.5 kilometers per hour

const2013 [10]4 years ago

6 0

Average speed =

(total distance covered) / (total time to cover the distance) .

Total distance covered = (94km + 65 km) = 159 km.

Total time = (3 hr + 3 hr) = 6 hours

Average speed = (159 km) / (6 hours) = 26.5 km/hr .

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You may have noticed runaway truck lanes while driving in the mountains. These gravel-filled lanes are designed to stop trucks t

Sladkaya [172]

Answer:

0.767

Explanation:

The work done on the truck by the frictional drag force is given by

$W=-Fd$

where

F is the magnitude of the frictional force

d = 38.0 m is the maximum displacement allowed for the truck

The negative sign is due to the fact that the force of friction is opposite to the motion of the truck

The force of friction can also be written as:

$F=\mu mg$

where

$\mu$ is the coefficient of kinetic friction between the truck and the lane

m is the mass of the truck

g is the acceleration of gravity

So we can rewrite the work done as

$W=-\mu mg d$ (1)

According to the work-energy theorem, the work done by friction is equal to the change in kinetic energy of the truck:

$W=K_f - K_i = \frac{1}{2}mv^2-\frac{1}{2}mu^2$ (2)

where

v = 0 is the final velocity of the truck

u = 23.9 m/s is the initial velocity of the truck

By combining (1) and (2) we get

$-\frac{1}{2}mu^2 = -\mu mg d$

And solving for $\mu$ , we find the minimum coefficient of kinetic friction able to stop the truck in a distance d:

$\mu = \frac{u^2}{2gd}=\frac{23.9^2}{2(9.8)(38.0)}=0.767$

7 0

3 years ago

The process that enhances some properties of an object at the expense of other properties is called:

lidiya [134]

Answer:

The answer is: letter a, pop-out effect.

Explanation:

The "pop-out effect" is a phenomenon which allows the person's precognitive processes to detect a<em> visual stimulus that is potentially the most meaningful one</em> in a person's spatial field of attention. The pop-up effect occurs when a person distinguishes one object from the rest.

For example, when a child chooses among pictures in different colors, it is common for the child to point at colored pictures rather than grayscale pictures. This is an example of a pop-out effect. <u>The properties of the colored pictures is more preferred by the child thus, causing him not to choose or mind the grayscale images.</u>

Thus, this explains the answer.

6 0

3 years ago

How many kj of heat are needed to completely melt 144 g of titanium metal, given that the metal is at its melting point? the hea

Elina [12.6K]

Given, mass of titanium metal = 144 g

Heat of fusion of titanium metal= 18.7 J/g

Heat of fusion is the amount of heat energy needed to change the state of one gram of a substance from solid to liquid or vice-versa.

Thus, 18.7 J of heat is needed to melt one gram of titanium metal.

Therefore, heat needed to melt 144 g of titanium metal = 18.7×144

= 2692.8 J

8 0

3 years ago

Why are water storage tanks usually built on towers or hilltops??

Komok [63]

Because when you open the faucet, you want the water to
rush out with pressure, not just dribble or ooze out. The
water has to be supplied to the user with pressure. Either
you supply it from a height, or else you'll need to use pumps
to make the pressure.

8 0

3 years ago

What is acceleration

SVETLANKA909090 [29]

Answer:

Explanation:

Acceleration is the rate of change of velocity. Usually, acceleration means the speed is changing, but not always. When an object moves in a circular path at a constant speed, it is still accelerating, because the direction of its velocity is changing.

6 0

3 years ago