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2 years ago

10. Calculate the kinetic energy of a running back that has a mass of 80 kg and

Physics

1 answer:

EastWind [94]2 years ago

5 0

Answer:

The answer is

Explanation:

The kinetic energy of an object given it's mass and velocity can be found by using the formula

$KE = \frac{1}{2} m {v}^{2}$

where

m is the mass

v is the velocity

From the question

m = 80 kg

v = 8 m/s

The kinetic energy is

$KE = \frac{1}{2} \times 80 \times {8}^{2} \\ = 40 \times 64$

We have the final answer as

Hope this helps you

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A system of two objects has ΔKtot = 6 J and ΔUint = -5 J. Part A How much work is done by interaction forces? Express your answe

Elina [12.6K]

A) +5 J

B) +1 J

Explanation:

The internal forces (interaction forces) acting on a system do not change the mechanical energy (sum of potential and kinetic energy) of the system.

However, these forces are responsible for converting the energy from one form into another; the work done by these forces is equal to the amount of energy converted from one form into the other.

In this problem, we have:

$\Delta U=-5 J$ is the loss in potential energy of the system

$\Delta K=+6 J$ is the gain in kinetic energy of the system

By looking at these numbers, this means that the internal forces have converted 5 J of energy from potential energy into kinetic energy (while the additional +1 J missing is due to external forces, as explained in part B).

Therefore, the work done by internal forces is

W = +5 J

First of all, we calculate the change in mechanical energy of the system.

The mechanical energy of a system is the sum of its kinetic energy (K) and its potential energy (U):

$E=K+U$

So, the change in mechanical energy is equal to the sum of the changes of kinetic energy and the changes of potential energy:

$\Delta E= \Delta K + \Delta U$

In this problem:

$\Delta K=+6 J$

$\Delta U=-5 J$

So, the change in mechanical energy is:

$\Delta E=+6+(-5)=+1 J$

According to the work-energy theorem, the work done by external forces on a system is equal to the change in mechanical energy of the system: therefore in this case, the work done by external forces is

$W=\Delta E=+1 J$

5 0

3 years ago

What is a type of force that results from turning a corner on a bicycle?

Romashka-Z-Leto [24]

This force is centripetal force. it is the force that will hold the rider in the circular path and prevent him from skidding off. It is equal to the friction between the tyres and the road if no banking has been done on the road at the corner.

6 0

3 years ago

Read 2 more answers

Which of the following are likely to be physical changes to an object?

tatuchka [14]

Answer:

The correct option is 'd': The change in shape of an object.

Explanation:

Since by definition physical change is defined as a change that changes only the form of an object or substance and producing no change in the chemical composition of the substance. Physical changes are reversible in nature.

As we can see from all the options the change in the shape of the object is a reversible change as we can always remold any substance in any shape, thus it confirms to a physical change.

The change in the molecular composition of an object is a hallmark of a chemical reaction thus indicates a chemical change.

The smell change in an object is an indication of a chemical change in the object hence is not a physical change.

7 0

3 years ago

A 5-kg can of paint is sitting on top of a 2-meter high step ladder. How much work did you do to move the can of paint to the to

Xelga [282]

98J

Explanation:

Given parameters:

Mass of paint can = 5kg

Height of ladder = 2m

Unknown:

Work done = ?

Potential energy = ?

Solution:

Work done in moving the paint is the force applied under gravity to move it through the give height.

Potential energy is the energy due the position of a body at rest.

For this body:

The work done in moving the paint = Potential energy at the top of ladder = m x g x h

m is the mass of the pain can

g is the acceleration due to gravity

h is the height of the building

Input the variables;

Work done = 5 x 9.8 x 2 = 98J

Potential energy = 98J

learn more:

Potential energy brainly.com/question/10770261

#learnwithBrainly

3 0

3 years ago

Unless indicated otherwise, assume the speed of sound in air to be v = 344 m/s. A pipe closed at both ends can have standing wav

uranmaximum [27]

Answer:

68.8 Hz

137.6 Hz, 206.4 Hz

Explanation:

L = Length of tube = 2.5 m

v = Velocity of sound in air = 344 m/s

Distance between nodes is given by

$L=\dfrac{\lambda}{2}+m\dfrac{\lambda}{2}\\\Rightarrow \dfrac{\lambda(n+1)}{2}=L\\\Rightarrow \lambda=\dfrac{2L}{n+1}$

Where n = 0, 1, 2, 3, ...

Making n+1 = n

$\lambda=\dfrac{2L}{n}$

where n = 1, 2, 3 .....

For fundamental frequency n = 1

$\lambda=\dfrac{2\times 2.5}{1}\\\Rightarrow \lambda=5\ m$

Frequency is given by

$f=\dfrac{v}{\lambda}\\\Rightarrow f=\dfrac{344}{5}\\\Rightarrow f=68.8\ Hz$

The fundamental frequency is 68.8 Hz

First overtone

$2f=2\times 68.8=137.6\ Hz$

Second overtone

$3f=3\times 68.8=206.4\ Hz$

The overtones are 137.6 Hz, 206.4 Hz

4 0

3 years ago