Beating a carpet with a carpet beater.

Alana is skateboarding at 19 km/h and throws a tennis ball at 11 km/h to her friend Oliver who is behind her leaning against a w

NNADVOKAT [17]

The speed of the tennis ball is 8 km/h when Alana throws the ball behind at the speed of 11 km/h.

<h3>What is the frame of reference?</h3>

It is a point from where the motion is observed. The speed changes with the frame of reference.

For the person standstill on the sidewalk, If Alana throw the ball in the front direction, The speed will be,

19+11 = 30 km/h

It Alana just leave the ball, the speed,

19 +0 = 19 km/h

If Alana throws the ball behind her at the speed of 19 km/h. The speed of the ball for a sidewalk observer,

19 +(-19 ) = 0 km/h

Thus, when Aana throw the ball behind the velocity will be negative,

So,

19 + (-11 ) = 8 km/h

Therefore, the speed of the tennis ball is 8 km/h when Alana throws the ball behind at the speed of 11 km/h.

Learn more about Frame of reference:

brainly.com/question/9820962

8 0

2 years ago

Only using 10 ohm resistors come up with a way to make a battery catch fire

Margaret [11]

They catch fire with the ohm with the light from the gas with the heat and gas from radiation elects from the chemicals mixed

6 0

3 years ago

A bicycle is heading West. It goes 5000m in 500s what's its velocity

dybincka [34]

There are several information's of immense importance already given in the question. Based on the given information's the answer to the question can easily be determined.
Distance covered by the bicycle = 5000 meter
Time taken by the bicycle to reach the distance = 500 second.
Velocity of the bicycle = Distance / Time taken
= 5000/500 meter/second
= 50 meter/second
So the velocity of the bicycle is 50 meter per second. I hope the procedure is clear enough for you to understand. In future you can always use this procedure for solving similar problems.

8 0

3 years ago

A strip of copper 190 µm thick and 4.20 mm wide is placed in a uniform magnetic field of magnitude B = 0.78 T, that is perpendic

Veronika [31]

Answer:

V = 9.682 × 10^(-6) V

Explanation:

Given data

thick = 190 µm

wide = 4.20 mm

magnitude B = 0.78 T

current i = 32 A

to find out

Calculate V

solution

we know v formula that is

V = magnitude× current / (no of charge carriers ×thickness × e

here we know that number of charge carriers/unit volume for copper = 8.47 x 10^28 electrons/m³

so put all value we get

V = magnitude× current / (no of charge carriers ×thickness × e

V = 0.78 × 32 / (8.47 x 10^28 × 190 × 1.602 x 10^(-19)

V = 9.682 × 10^(-6) V

3 0

3 years ago

A girl coasts down a hill on a sled, reaching level ground at the bottom with a speed of 7.4 m/s. The coefficient of kinetic fri

Amanda [17]

Answer: 62.22 meters

Explanation:

Two solve this, we need to know first how the Sled interact with the snow. While the Sled runs over the snow, the snow opposes to it movement, this is call friction. Frictions creates is a force that goes against any movement and is caused by the interaction between surfaces.

Friction can be calculated using the following equation:

Friction's Force (Ff) = m*N

Where m is the Frictions coficient and N is call Normal, which is a force created by the contact between any weight and a surface. Because the sled is and the surface are totally horizontal, the Normal is equal to the Sled's Weight.

So for this case, we can calculate the Friction's Force:

Ff = 0.045 * 735 N

Ff = 33,07 N

This force will cause a negative acceleration the Sled causing it to slow down and finally stop. To know this accelaration we can use the following equation:

Force (F) = Mass (m) * Accelaration (a)

Looking for the accelaration:

Acceleration (a) = F / M

As a side note:

Mass (M) = F / a (1)

Where we know that F is equal to our Friction Force (Ff) and the Mass for the girl and the Sled can be obtained using the previous equation (1) like this

Girl and sled Mass (M) = 735 N / (9.81 m/s)

M = 74,92 Kg

This is posible, because the Girl and The Sled are aplying a Force on the ground equal to 735 N. The accelartion for their mass is the gravity

Now, with the mass we can found the Accelaration caused by friction:

Acceleration (a) = Ff / M

Accelaration (a) = 33,07 N / 74,92 Kg

a = 0,44 $m/s^{2}$

To know how far the Sled travel we can use the following equation:

$V_{f} ^{2} = V_{0} ^{2} + 2ax$

Where Vf is the Final Velocity, which is when the sled finally stops (Vf = 0), Vo is the Initial Speed of the Sled equal to 7.4 m/s and a is equal to the negative accelaration that causes the friction.

$(0)^{2} = (7.4 m/s)^{2} + 2(-0,44)x$

Searching for x:

$x = \frac{0 - (7.4 m/s)^{2} }{-0.88}$

$x = 62.22 meters$

The girls will run over the snow 62.22 meter until finally stopping

4 0

3 years ago