a) As observed from the shore, the speed of the boats can be expressed as the vector sum, of the boat speed relative to the water and the river speed relative to the shore, as follows:

vb₁s = vb₁w + vrs

In one case, the boat is moving in the same direction as the water:

vb₁s = vb₁w + vrs = 7.0 m/s (1)

For the other boat, it is clear that is moving in an opposite direction:

vb₂s = vb₂w - vrs = 4.9 m/s (2)

As we know that vb₁w = vb₂w, adding both sides, we can remove the river speed from the equation, as follows:

vb₁w = vb₂w = $\frac{7.0 m/s + 4.9 m/s}{2} =5.95 m/s$

b) Replacing this value in (1) and solving for vriver, we have:

vriver = 7.0 m/s - 5.95 m/s = 1.05 m/s

(we could have arrived to the same result subtracting both sides in (1), and (2))

3 0

3 years ago

A trumpet player, using her ear, hears 5 beats per second when she plays a note on her trumpet and simultaneously sounds a 440 H

german

<h2>Frequency of trumpet wire = 445 Hz</h2>

Explanation:

The given frequency of tuning fork is 440 Hz . It produces 5 beats with trumpet wire . That means , the frequency of wire can be 440 ± 5

It can be either 445 or 435

Now the length of wire is increased , by which its frequency decreases . Because frequency is inversely proportional to length of wire .

If we decrease the frequency in 435 , the difference between tuning fork frequency and wire frequency will become greater than 5 even . So it cannot produce 3 beats with it .

If we decrease frequency from 445 , it can become 443 Hz . It gives 3 beat with the tuning fork as given .

Thus the initial frequency of wire is 445 Hz

4 0

3 years ago

What’s the difference between mechanical and chemical weathering

vampirchik [111]

Answer:

Mechanical weathering is the physical breakdown of rock into smaller pieces. Chemical weathering is the breakdown of rock by chemical processes.

Explanation:

Mechanical weathering (also called physical weathering) breaks rock into smaller pieces. These smaller pieces are just like the bigger rock, just smaller. That means the rock has changed physically without changing its composition. The smaller pieces have the same minerals, in just the same proportions as the original rock.

Chemical weathering is the other important type of weathering. Chemical weathering is different from mechanical weathering because the rock changes, not just in size of pieces, but in composition Chemical weathering works through chemical reactions that cause changes in the minerals.

5 0

3 years ago

the current flowing in an appliance connected to a 120V source is 2A. How many kilowatt-hours of electrical energy does the appl

skad [1K]

Answer:

0.96 kWh

Explanation:

First of all, we can find the power of the appliance using the formula:

$P=VI$

where

V = 120 V is the voltage of the source

I = 2 A is the current

Substituting,

$P(120 V)(2 A)=240 W = 0.24 kW$

Now we want to find the amount of energy used by the applied in a time of

t = 4 h

The amount of energy is given by

$E=Pt$

where

P = 0.24 kW

t = 4 g

Substituting,

$E=(0.24 kW)(4 h)=0.96 kWh$

8 0

3 years ago