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kati45 [8]
2 years ago
7

Find :

Physics
1 answer:
Pepsi [2]2 years ago
8 0

Answer:

Explanation:

b) Gravity reduces the initial upward velocity to zero in a time of

t = v/g = 40/10 = 4 s

a) h =  v₀t + ½gt² = 40(4) +  ½(-10)4² = 80 m

or

v² = u² + 2as

h = (0² - 40²) / 2(-10) = 80 m

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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 worker pushes a crate horizontally across a warehouse floor with a force of 245 N at an angle of 55 degrees below the horizont
aev [14]

Answer:

option A

Explanation:

given,

For exerted by the worker = 245 N

angle made with horizontal = 55°

we need to calculate Force which is not used to move the crate = ?

Movement of crate is due to the horizontal component of the force.

Crate will not move due to vertical force acting on the it.

F_y = F sin \theta

F_y = 245\times sin 55^0

F_y =200.69

hence, worker's force not used to move the crate is equal to 200.69

The correct answer is option A

6 0
3 years ago
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Galaxies contain on average about 100 billion stars. These stars are held together in galaxies by the force of _________________
Butoxors [25]
Its not a or c just saying
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All the following statements about DC current are true except:
trapecia [35]

Answer:

Is considered as not as dangerous as AC

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A boy pulls a wagon with a force of 6N east as another boy pushes it with a force of 8 N
NARA [144]

Answer:

14N

Explanation:

4 0
2 years ago
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