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3 years ago

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3. How long will it take a ball to reach the ground if it falls from a cliff 25 m tall (starting from rest)? What if the ball we

re given an initial horizontal velocity of 5 m/s? please help,thanks

1 answer:

Nady [450]3 years ago

4 0

Answer:

2.26 s

Explanation:

Let's take down to be positive.

Given (in the y direction):

Δy = 25 m

v₀ = 0 m/s

a = 9.8 m/s²

Find: t

Δy = v₀ t + ½ at²

25 m = (0 m/s) t + ½ (9.8 m/s²) t²

25 = 4.9t²

t = 2.26 s

If the ball instead had an initial horizontal velocity of 5 m/s, its initial vertical velocity is still 0 m/s. So the time to fall is still 2.26 s.

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At t = 0, object A is dropped from the roof of a building. At the same instant, object B is dropped from a window 10 m below the

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Answer:

Explanation:

Given two objects are dropped simultaneously

Object A is 10 m higher than object B therefore

Distance covered by object A is given by

$y_a(t)$ is given by

$y=ut+\frac{1}{2}at^2$

where y=displacement

u=initial velocity

a=acceleration

t=time

$y_a(t)=0+0.5gt^2--1$

for object B

$y_b(t)=0+0.5gt^2--2$

Subtract 1 and 2 we get

$y_a(t)-y_b(t)=0$

i.e. they will travel equal distance in equal time and distance between them remain 10 m until object B hits the ground

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How to calculate kinetic energy given mass and velocity

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In classical mechanics, kinetic energy (KE) is equal to half of an object's mass (1/2*m) multiplied by the velocity squared. For example, if a an object with a mass of 10 kg (m = 10 kg) is moving at a velocity of 5 meters per second (v = 5 m/s), the kinetic energy is equal to 125 Joules, or (1/2 * 10 kg) * 5 m/s2.

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2 years ago

A grinding wheel is a uniform cylinder with a radius of 8.65 cm and a mass of 0.400 kg . Calculate its moment of inertia about i

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Answer:

I = 1.5*10⁻³ kg*m²

Explanation:

It can be showed that the moment of inertia (or rotational inertia) for a uniform cylinder of mass m and radius r, respect an longitudinal axis going through its center (parallel to the height of the cylinder) can be written as follows:

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3 years ago

A Neglecting air resistance, a ball projected straight upward so it remains in the air for 10 seconds needs an initial speed of

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Answer:

The initial velocity is 50 m/s.

(C) is correct option.

Explanation:

Given that,

Time = 10 sec

For first half,

We need to calculate the height

Using equation of motion

$v^2=u^2+2gh$

$h =\dfrac{v^2}{2g}$ ....(I)

For second half,

We need to calculate the time

Using equation of motion

$h =ut+\dfrac{1}{2}gt_{2}^2$

$h=0+\dfrac{1}{2}gt_{2}^2$

$t_{2}=\sqrt{\dfrac{2h}{g}}$

Put the value of h from equation (I)

$t_{2}=\sqrt{\dfrac{2\times v^2}{g^2}}$

$t_{2}=\dfrac{v}{g}$

According to question,

$t_{1}+t_{2}=10$

$t_{1}=t_{2}$

Put the value of t₁ and t₂

$\dfrac{v}{g}+\dfrac{v}{g}=10$

$\dfrac{2v}{g}=10$

$v=\dfrac{10\times g}{2}$

Here, g = 10

The initial velocity is

$v=\dfrac{10\times10}{2}$

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Hence, The initial velocity is 50 m/s.

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3 years ago