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4 years ago

A motorist travels for 3.0 h at 80 km/h and 2.0 h at 100 km/h. What is her average speed for the trip?

Physics

2 answers:

USPshnik [31]4 years ago

8 0

Answer:

The motorist average speed for the trip is 88 km/h

Explanation:

In order to know her average speed, we have to refer to the following ecuation:

<V> (average speed) = $\frac{Vfinal+Vinital}{2}$

So, according to that, we know that the motorist has been having a speed of 80km/h during 3 hours, and a speed of 100 km/h during 2 hours. It means that her speed during all the travel is 5 hours.

Then, we have to affect the 5 hours to the inicial and final speed as follows:

First, at 80 km/h, she travels during 2 hours so:

3h*80km/h= 240 km

And then, at 100 km/h:

2h*100km/h= 200 km

Which leads us to:

initial speed: 240 km/ 5 h= 48 km/h

and final speed of: 200 km/ 5 h= 40 km/h

Then, the average speed is:

<V> = 48 km/h + 40 km/h = 88 km/h

Volgvan4 years ago

6 0

3x80=240
2x100=200
240+200/5=88 k/hr
☺☺☺☺

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Answer:

Normal Force is usually perpendicular to the movement and static friction usually means that there is no movement.

Explanation:

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Normal force is usually perpendicular to the movement, so there is no component in the direction of the displacement. This is why it is zero in most circumstances.

Static friction on the other hand, usually means that there is no movement at all (it's static). It means that there is no displacement between the object and ground (in most cases). If there is no displacement, there is no work.

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3 years ago

A block has two strings attached to it on opposite ends. One string has a force of 5 N,

juin [17]

Unless you have a diagram to include or any other additional info, I'll assume the block is being pulled by two opposing forces along the horizontal surface.

Horizontally, the block is under the influence of

• one rope pulling in one direction with magnitude 15 N,

• the other rope pulling in the opposite direction with mag. 5 N, and

• friction, opposing the direction of the block's motion, with mag. 3 N.

It stands to reason that the block is accelerating in the direction of the larger pulling force.

(A) By Newton's second law, we have

15 N + (-5 N) + (-3 N) = m (1 m/s²)

where m is the mass of the block. Solve for m :

7 N = m (1 m/s²)

m = (7 N) / (1 m/s²)

m = 7 kg

(B) The friction force is proportional to the normal force, so that if f is the mag. of friction and n is the mag. of the normal force, then f = µ n where µ is the coefficient of friction.

The block does not bounce up and down, so its vertical forces are balanced, which means the normal force and the block's weight (mag. w) cancel out:

n + (-w) = 0

n = w

n = m g

where g = 9.8 m/s² is the mag. of the acceleration due to gravity.

n = (7 kg) (9.8 m/s²)

n = 68.6 N

Then

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3 years ago

Một dây dẫn đặt trong không khí có dòng điện I = 12A chạy qua, được gấp thành hình vuông cạnh a = 10cm. Xác định vectơ cường độ

disa [49]

Answer:

The net magnetic field ta the center of square is $1.36\times10^{-4} T$ .

Explanation:

Current, I = 12 A , side ,a = 10 cm = 0.1 m

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The magnetic field is given by

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Net magnetic field at the center of the square is

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3 years ago

A person is standing on a raft; their

krok68 [10]

Answer:

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Explanation:

The question relates to Archimedes' principle which states that the buoyant force experienced by an object immersed in a fluid is equal to the weight of (the force of gravity on) the displaced fluid

The given parameters are;

The combined mass of the person and the raft, m = 233 kg

The liquid on which the raft is located = Water

The density of water, $\rho _{water}$ = 1000 kg/m³

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Where;

m = The mass of the object

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Given that the raft is on the surface of the water (floating), the buoyant force is equal to the combined weight of the person and the raft = 233 kg

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Answer:

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