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Vesna [10]
3 years ago
9

If only an external force can change the velocity of a body, how can the internal force of the brakes bring a car to rest? 1. It

is the driver, not the car itself who causes the breaking, so it is an external force. 2. The engine is stopped, so the car has no force to run further. 3. Some internal forces can change the velocity of a body. 4. It is the force of the road on the tires (an external force) that stops the car.
Physics
1 answer:
RoseWind [281]3 years ago
3 0

Answer:

4. It is the force of the road on the tires (an external force) that stops the car.

Explanation:

If there is no friction between the road and the tires, the car won't stop.

You can see this, for example, when there is ice on the road. You can still apply the brakes (internal force), but since there is no friction (external force) the car won't stop.

The force of the brakes on the wheels is not what makes the car stop, it is the friction of the road against still tires that makes it stop.

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Definition of Newton’s first law of motion
kipiarov [429]

Newton's first law of motion - sometimes referred to as the law of inertia. Newton's first law of motion is often stated as. An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

3 0
3 years ago
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13. A step up transformer has 250 turns on its primary and 500 turns on it secondary. When the primary is connected to a 200 V a
Lisa [10]

Answer:

The output power is 2 kW

Explanation:

It is given that,

Number of turns in primary coil, N_p=250

Number of turns in secondary coil, N_s=500

Voltage of primary coil, V_p=200\ V

Current drawn from secondary coil, I_s=5\ A

We need to find the power output. It is equal to the product of voltage and current. Firstly, we will find the voltage of secondary coil as :

\dfrac{N_p}{N_s}=\dfrac{V_p}{V_s}

\dfrac{250}{500}=\dfrac{200}{V_s}

V_s=400\ V

So, the power output is :

P_s=V_s\times I_s

P_s=400\ V\times 5\ A

P_s=2000\ watts

or

P_s=2\ kW

So, the output power is 2 kW. Hence, this is the required solution.

8 0
3 years ago
Emma is running for the bus. She runs 100 metres in 25 seconds. Calculate her speed
Afina-wow [57]

Answer:

25km/h

is that the full question

8 0
3 years ago
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Suppose a grower sprays (8.2x10^1) kg of water at 0 °C onto a fruit tree of mass 180 kg. How much heat is released by the water
____ [38]

Since there is no temperature change which drives heat flow, thus no heat will be released by the water.

<h3>Heat released by the water when it freezes</h3>

The heat released by the water when it freezes is calculated as follows;

Q = mcΔФ

where;

  • m is mass of water
  • c is specific heat capacity of water
  • ΔФ is change in temperature = Фf - Фi

when water freezes, the temperature, Фf = 0 °C

Q = 82 x 4200 x (0 - 0)

Q = 0

Since there is no temperature change which drives heat flow, thus no heat will be released by the water.

Learn more about heat flow here: brainly.com/question/14437874

6 0
2 years ago
A joule equals the amount of work done on an object when a force _______ displaces that object ______.
Anastaziya [24]

Answer:

A joule equals the amount of work done on an object when a force <u>of</u><u> </u><u>1</u><u> </u><u>Newton</u><u> </u> displaces that object <u>1</u><u> </u><u>metre</u>

3 0
2 years ago
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