Physics, 16.12.2020 16:50 chloerodgers56

. A rubber ball dropped from a height of 20m (g=10m/s2) falls on the roof of an elevator
going up at 2 m/s. If the collision of the ball
with the elevator is elastic, the ball
rebounds with a velocity of

Answers: 3

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Answer from: Lolgirl5862

24 m/s

Explanation:

Given that the height of the ball from the elevator, h=20 m

The acceleration due to gravity, g=10 m/ s^2

The initial velocity of the ball is zero, so, by using the equation of the motion v^2=u^2+2as the velocity of the ball, v, when reached the elevator,

$v^2=0+2\times 10 \times 20 \times h$

$v=\sqrt{400}=20$ m/s

The velocity of the ball just before the collision is 20 m/s in the downward direction.

The velocity of the lift just before the collision is 2 m/s in the upward direction.

As the ball and the lift moves in the opposite direction, so the speed of approach = 20+2=22 m/s.

Assuming that there is negligible change in the speed of the lift, so the velocity of the lift after the collision is 2 m/s

Let the velocity of the ball after the collision is V_2 m/s in the direction of the velocity of the lift.

So, the speed of the separation =V_2 -2

As the collision is elastic, so the coefficient of restitution, $\mu=1$

$\mu = \frac {\text{Speed of seperation}}{\text{speed of approach}}$

$\Rightarrow 1=\frac{V_2-2}{22} \\\\\Rightarrow V_2-2=22 \\\\\Rightarrow V_2=22+2 \\\\$

$\Rightarrow V_2=24$ m/s

Hence, the ball rebounds with a velocity of 24 m/s.

Answer from: Quest

distance on the y-axis and time on the x-axis.

explanation:

the instantaneous velocity = change in position/time taken

the slope of the graph should give instantaneous velocity.

slope of a graph = change in value of y -axis / change in values of x -axis

comparing both the equations

change in value of y -axis = change in position

change in values of x -axis = time taken

so position values should be on the y axis and time values should be on the x axis.

distance on the y-axis and time on the x-axis.

Answer from: Quest

electromagnetic shielding is the practice of reducing the electromagnetic field in a space by blocking the field with barriers made of conductive or magnetic materials. shielding is typically applied to enclosures to isolate electrical devices from their surroundings, and to cables to isolate wires from the environment through which the cable runs. electromagnetic shielding that blocks radio frequency electromagnetic radiation is also known as rf shielding.

the shielding can reduce the coupling of radio waves, electromagnetic fields and electrostatic fields. a conductive enclosure used to block electrostatic fields is also known as a faraday cage. the amount of reduction depends very much upon the material used, its thickness, the size of the shielded volume and the frequency of the fields of interest and the size, shape and orientation of apertures in a shield to an incident electromagnetic

from wikipedia

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. A rubber ball dropped from a height of 20m (g=10m/s2) falls on the roof of an elevator
going...

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