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2 years ago

A woman on a bridge 90.0 m high sees a raft floating at

Physics

1 answer:

Stells [14]2 years ago

7 0

Answer:

0.93 m/s

Explanation:

t = Time taken

u = Initial velocity = 0

v = Final velocity

s = Displacement = 90 m

a = Acceleration = 9.81 m/s²

$s=ut+\frac{1}{2}at^2\\\Rightarrow 90=0\times t+\frac{1}{2}\times 9.81\times t^2\\\Rightarrow t=\sqrt{\frac{90\times 2}{9.81}}\\\Rightarrow t=4.3\ s$

So, the raft covered 6-2 = 4 m in 4.3 seconds

Speed = Distance / Time

$\text{Speed}=\frac{4}{4.3}=0.93\ m/s$

Speed of the raft is 0.93 m/s

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A gymnast dismounts the uneven parallel bars with some angular momentum about her transverse axis. Just after release, she is in

Luda [366]

Answer:

a. Her moment of inertia increases and she rotates slower.

Explanation:

As we know that initially when she starts her motion she is in piked position due to which her whole mass is concentrated near the axis of rotation

So here the rotational Inertia of her body will be smaller

Now when is comes closer to the position of landing she extends into layout position due to which her mass will move away from the axis of rotation

Due to this the rotational inertia of her body will increase

now we know that there is no external torque on the system

so here angular momentum must be conserved

So we will have

$I\omega = constant$

so if rotational inertia is increasing then angular speed must be slower

so correct answer will be

a. Her moment of inertia increases and she rotates slower.

7 0

2 years ago

A man holding 7N weight moves 7m horizontal and 5m vertical , find the work done

SashulF [63]

Answer:

35 J

Explanation:

The man is holding the box: this means that he is applying a force vertically upward, to balance the weight of the box (which pushes downward).

Therefore, we can ignore the horizontal displacement of the man, because the force applied (vertically upward) is perpendicular to that displacement (horizontal), so the work done for that is zero.

So, only the vertical motion contributes to the work. The work done by the man is equal to the gain in gravitational potential energy of the box, so:

$W=(mg)\Delta h$

where

$mg=7 N$ is the weight of the box

$\Delta h=5 m$ is the vertical displacement

Substituting, we find

$W=(7N)(5 m)=35 J$

8 0

2 years ago

The voltage across the terminals of a 9.0 v battery is 8.5 v when the battery is connected to a 60 ω load. part a what is the ba

snow_lady [41]

Refer to the diagram shown below.

i = the current in the circuit., A
R₁ = the internal resistance of the battery, Ω
R₂ = the resistance of the 60 W load, Ω

Because the resistance across the battery is 8.5 V instead of 9.0 V, therefore
(R₁ )(i A) = 9 - 8.5 = (0.5 V)
R₁*i = 0.5 (10

Also,
R₂*i = 9.5 (2)

Because the power dissipated by R₂ is 60 W, therefore
i²R₂ = 60
From (2), obtain
i*9.5 = 60
i = 6.3158 A

From (1), obtain
6.3158*R₁ = 0.5
R₁ = 0.5/6.3158 = 0.0792 Ω = 0.08 Ω (nearest hundredth)

Answer: 0.08 Ω