20.0 m [N] - 15 m [S20degreesE]

Stels [109]

The time taken by the swimmer was 1 hour.

Why?

Since the swimmer is maintaining an angle of 150° while he was swimming, there were two components of the speed (horizontal and vertical). If we want to calculate the time taken by him to cross the river, we need to calculate the vertical speed and consider that the flow's speed is compensated by his horizontal speed.

We can calculate both components of the speed using the following formula:

$HorizontalSpeed=Speed*Cos(150\°)\\\\VerticalSpeed=Speed*Sin(150\°)$

Now, calculating we have:

$HorizontalSpeed=2\frac{Km}{h} *Cos(150\°)=-\sqrt{3} \frac{Km}{h} \\\\VerticalSpeed=2\frac{Km}{h} *Sin(150\°)=1\frac{Km}{h}$

Therefore, we have that the horizontal speed is compesating the flow's speed while his vertical speed is used to cross the river which is 1 Km wide.

Hence, we have that the tame taken is:

$Time=\frac{RiverWidth}{VerticalSpeed}=\frac{1Km}{1\frac{Km}{h} } =1h$

Have a nice day!

7 0

3 years ago

In her hand, a softball pitcher swings a ball of mass 0.245 kg around a vertical circular path of radius 59.8 cm before releasin

GuDViN [60]

Answer:

The velocity is $v_b = 20.17 \ m/s$

Explanation:

From the question we are told that

The mass of the ball is $m = 0.245 \ kg$

The radius is $r = 59.8 \ cm = 0.598 \ m$

The force is $F = 30.9 \ N$

The speed of the ball is $v = 16.0 \ m/s.$

Generally the kinetic energy at the top of the circle is mathematically represented as

$K_t = \frac{1}{2} * m * v^2$

=> $K_t = \frac{1}{2} * 0.245 * 16.0 ^2$

=> $K_t = 31.36 \ J$

Generally the work done by the force applied on the ball from the top to the bottom is mathematically represented as

$W = F * d$

Here d is the length of a semi - circular arc which is mathematically represented as

$d = \pi * r$

So

$W = 30.9 * 0.598$

$W = 18.48 \ J$

Generally the kinetic energy at the bottom is mathematically represented as

$K_b = \frac{1}{2} * m * v_b^2$

=> $K_b = \frac{1}{2} * 0.245 * v_b^2$

=> $K_b = 0.1225 * v_b^2$

From the law of energy conservation

$K_t + W =K_b$

=> $31.36+ 18.48 = 0.1225 * v_b^2$

=> $v_b = 20.17 \ m/s$

3 0

3 years ago

A rocket passing the earth with high speed will look shorter for the stationary observer measuring the size on earth than travel

neonofarm [45]

Answer:

True

Explanation:

This can be explained by the special theory of relativity for length contraction.

Length contraction is observed in the direction of motion of an object when an object moves with speed closer to the speed of light.

The length of the rocket in this case, appears shorter to the observer on earth in the stationary reference frame which is improper frame whereas the traveler in the rocket is in the same inertial frame which is proper for the rocket's size measurement.

5 0

3 years ago

Heat energy is transferred by conduction whenever molecules?

Rama09 [41]

<em>The heat transfer by conduction occurs due to the collision between the molecules in the substance.</em>

Explanation:

The heat transfer between the substances or in a medium is carried out by means of three methods.

Conduction
Convection
Radiation

The conduction is the process of transfer of heat within the substance by transferring the heat one by one to each molecule throughout the substance by colliding with the neighboring molecule. This method prevails in the transfer of heat in the solids.

The convection is the process of transfer of heat in which the source of heat is used to heat a particular bunch of molecules or a layer of the substance and then that layer moves away from the source and lets other molecule to come close to the layer. This method of heating is used in liquids.

The radiation is the process of transfer of heat in the medium by means of the energy carried by the radiation. This process of heating is used for the heating of the gases in the medium.

Thus, <em>The heat transfer by conduction occurs due to the collision between the molecules in the substance.</em>

Learn More:

1. Which one is a compound machine brainly.com/question/9060219

2. Equinoxes occur when brainly.com/question/1000562

3. Explanation for the salinity of ocean water brainly.com/question/2752734

Answer Details:

Grade: Middle School

Subject: Physics

Chapter: Heat transfer

Keywords:

heat energy, transferred, conduction, convection, radiation, molecules, solids, liquids, medium, substance, transfer.

8 0