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shusha [124]
3 years ago
6

imagine riding a single-speed bicycle. why do you have to push harders on the pedals to start the bicycle moving than to keep it

moving at constant velocity ?
Physics
1 answer:
Flura [38]3 years ago
3 0
A large force is required to accelerate the mass of the bicycle and rider. Once the desired constant velocity is reached, a much smaller force is sufficient to overcome the ever-present frictional forces. 
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Alex is asked to move two boxes of books in contact with each other and resting on a rough floor. He decides to move them at the
Over [174]

Answer:

Part a)

a= 0.32 m/s^2

Part b)

F_c = 3.6 N

Part c)

F_c = 5.5 N

Explanation:

Part a)

As we know that the friction force on two boxes is given as

F_f = \mu m_a g + \mu m_b g

F_f = 0.02(10.6 + 7)9.81

F_f = 3.45 N

Now we know by Newton's II law

F_{net} = ma

so we have

F_p - F_f = (m_a + m_b) a

9.1 - 3.45 = (10.6 + 7) a

a = \frac{5.65}{17.6}

a= 0.32 m/s^2

Part b)

For block B we know that net force on it will push it forward with same acceleration so we have

F_c - F_f = m_b a

F_c = \mu m_b g + m_b a

F_c = 0.02(7)(9.8) + 7(0.32)

F_c = 3.6 N

Part c)

If Alex push from other side then also the acceleration will be same

So for box B we can say that Net force is given as

F_p - F_f - F_c = m_b a

9.1 - 0.02(7)(9.8) - F_c = 7(0.32)

F_c = 9.1 - 0.02 (7)(9.8) - 7(0.32)

F_c = 5.5 N

3 0
3 years ago
An elaborate pulley consists of four identical balls at the ends of spokes extending out from a rotating drum. A box is connecte
Klio2033 [76]

Answer:

its speed will be less than V

Explanation:

When the ball falls a distance d, its final kinetic energy plus rotational kinetic energy of the drum equals its initial potential energy.

K = U

With its speed V at the end of d, we have

1/2mV² + 1/2Iω² = mgd where I = rotational inertia of drum and balls, ω = angular speed of drum and balls and m = mass of box

1/2mV² + 1/2Iω² = mgd

1/2mV² = mgd - 1/2Iω²

V² = [2(mgd - 1/2Iω²)/m]

V = √[2(mgd - 1/2Iω²)/m]

When the four balls are moved inward closer to the drum, their rotational inertia increases and also its angular speed which thus causes an increase in rotational kinetic energy. But, since the box still falls the same distance of d, its final kinetic energy plus rotational kinetic energy of the drum plus balls still equals its initial potential energy

K = U

I' = new rotational inertia of drum and balls, ω' = new angular speed of drum and balls

With its new speed is now V' at the end of d,

1/2mV'² + 1/2I'ω'² = mgd

1/2mV'² = mgd - 1/2I'ω'²

V² = [2(mgd - 1/2I'ω'²)/m]

V' = √[2(mgd - 1/2I'ω'²)/m]

Since I' and ω' increase, the rotational kinetic energy of the drum and balls (1/2I'ω'²) increases. Thus, the difference (mgd - 1/2I'ω'²) < (mgd - 1/2Iω²) which implies that the kinetic energy of the box decreases. Hence, since its kinetic energy decreases, its speed V' also decreases.

So,  V' < V

So, its speed will be less than V.

3 0
3 years ago
A player prefers to make high passes that lift the puck above the ice. Which stick should the
Arte-miy333 [17]

Answer:

i dont know

Explanation:

hello

8 0
3 years ago
How many neutrons does element X have if its atomic number is 59 and its mass number is 164?
Y_Kistochka [10]
The mass is the number of n + p if you subtract p from mass you will find n
164 - 59 = 105
4 0
3 years ago
PHYSICSSS PLEASE HELP
Aleonysh [2.5K]

Answer:

1. 10.5 Kg

2. s/g

Explanation:

1. Determination of the mass of gasoline

Density of gasoline = 0.7 Kg/L

Volume of gasoline = 15 L

Mass of gasoline =?

The density of a substance is simply defined as the mass of the substance per unit volume of the substance. Mathematically, the density of a substance can be expressed as:

Density = mass / volume

With the above formula, we can obtain the mass of the gasoline as follow:

Density of gasoline = 0.7 Kg/L

Volume of gasoline = 15 L

Mass of gasoline =?

Density = mass / volume

0.7 = Mass of gasoline / 15

Cross multiply

Mass of gasoline = 0.7 × 15

Mass of gasoline = 10.5 Kg

2. Density has various units some are listed below:

I. Kilogram per litre (Kg/L)

II. Kilogram per cubic metre (Kg/m³)

III. Milligram per millilitre (mg/mL)

IV. Gram per millilitre (g/mL)

V. Gram per cubic centimetre (g/cm³)

Considering the options given in the question above, it is evident that second per gram (s/g) is not a unit of density because density is mass per unit volume.

3 0
3 years ago
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