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3 years ago

A dog is running at 15 m/s and then slows down to 10 m/s. It takes him two seconds to do this. What is the dog's acceleration

Physics

1 answer:

OLga [1]3 years ago

6 0

Explanation:

a = (Vf-Vi)/t

= (10m/s - 15m/s)/2s

a = -5 / 2 m/s^2

• so the dog diaccelerate at the rate of 5/2 m/s^2

hope it helps

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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

$W=\Delta E=+1 J$

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3 years ago

Measuring a liquid's volume indicated the capacity ______ of the holds it. The most common units for expressing liquid volumes a

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Answer:

Measuring, comparing and estimating liquid volumes are taught using metric units like liters and milliliters and customary units like quart, pints, gallons and more. Capacity is actually the amount of liquid in the container, which is also the volume of a liquid.

Explanation:

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Answer:

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W = Energy at earth surface - Potential energy (PE)

But PE = $-\frac{GMm}{R}$

Therefore: W = Energy at earth surface - $\frac{GMm}{R}$

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But $V=\sqrt{\frac{GM}{5R} }$

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