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3 years ago

a train travels 99 kilometers in 3 hours, and then 80 kilometers in 5 hours. What is it’s average speed?

Physics

1 answer:

Karolina [17]3 years ago

6 0

Average speed = (total distance covered) / (time to cover the distance)

Total distance covered = (99km + 80km) = 179 km

Time to cover the distance = 8 hours

Average speed = (179km / 8hours)

Average speed = 22.375 km/hour

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(a) A light-rail commuter train accelerates at a rate of 1.35 m/s2 . How long does it take to reach its top speed of 80.0 km/h,

Mashcka [7]

Answer:

(a) Time t = 16.46 sec

(b) Time t =13.466 sec

Explanation:

(a) As the train starts from rest its initial velocity u = 0 m/sec

Acceleration $a=1.35m/sec^2$

Final speed v = 80 km/hr

$80km/hr=\frac{80\times 1000}{3600sec}=22.22m/sec$

From first equation of motion v =u+at

So $t=\frac{v-u}{a}=\frac{22.22-0}{1.35}=16.46 sec$

(b) Now initial speed u = 22.22 m/sec

As finally train comes to rest so final speed v=0 m/sec

Deceleration $a=1.65m/sec^2$

So $t=\frac{v-u}{a}=\frac{0-22.22}{-1.65}=13.466 sec$

Final velocity v = 0 m/sec

Time t = 8.30 sec

So acceleration is given by

$a=\frac{v-u}{t}=\frac{0-22.22}{8.3}=-2.6771m/sec^2$

As acceleration is negative so it is a deceleration

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3 years ago

What subatomic particle acts like a mini-magnet?

Semenov [28]

The subatomic particles that acts like a mini-magnet is electron. Electrons are negatively charged sub atomic particles in an atom. The electron spin is a property of an electron that makes it behave like it's spinning; a spinning electron produces a magnetic field that makes it behave like a tiny magnet in an atom.

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3 years ago

The first law of motion applies to what?

lana66690 [7]

First law of motion- sometimes referred to as the law of inertia. An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

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3 years ago

Why are house keys usually made of metal rather than glass

kherson [118]

Explanation:

doesn’t corrode easily and is soft enough for inexpensive tools to cut to the needed individual patterns.

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3 years ago

Which type of lever is exemplified by the flexing of the forearm by the biceps brachii muscle?

ira [324]

Answer:

a third class lever

Explanation:

The third class or interpower lever is a lever that enables fast and dynamic movements. It places the power between the resistance and the support, so the resistance arm is longer than the power.

It is the most frequent type of lever in the human body and as an example we can put the action of the brachial biceps in the flexion of the elbow, where the biceps is inserted in the forearm between the elbow that is behind and the resistance that would be displaced towards the hand by the weight of the load attached to the weight of the forearm.

A good range of movements is achieved although with less force and is the most frequent type of lever in human movement, although the same joint can form different types of lever depending on the type of movement performed .

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3 years ago