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3 years ago

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A 63.0-kg man is riding an escalator in a shopping mall. The escalator moves the man at a constant velocity from ground level to

the floor above, a vertical height of 4.20 m. What is the work done on the man by (a) the gravitational force and (b) the escalator

1 answer:

Oliga [24]3 years ago

8 0

Answer:

Explanation:

Given that,

Mass of man =Mm=63kg

W=mg

W=63×9.81

W=618.03N

g=9.81m/s²

The escalator moves at a constant velocity, then this shows that it is not accelerating, then, a=0m/s²

Height escalator traveled

H=4.2m.

We assume that the weight of the escalator is negligible.

a. Work done by gravity

Work done by gravity is given as

Work done(gravity)=mgh

Since the work is done against gravity, then, g is negative

Then,

Work done(gravity)=-mgh

Work done(gravity)=-63×9.81×4.2

Work done(gravity)=-2595.726J

b. Work done by escalator

Using equation of motion to know the force pulling the escalator upward

ΣF = ma, but a=0

ΣF = 0

Only two force is acting on the in y axis, the Normal force and the weight

N-W=0

N=W

Since W=618.03N

Then, N=618.03

The normal is the force pulling the escalator upward

Then, the work done by escalator is given as

Work done=Force × distance

Work done=618.03×4.2

Work done= 2595.76J

Work done by escalator is 2595.76J

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Rasek [7]

Complete question is;

Using energy considerations and assuming negligible air resistance, show that a rock thrown from a bridge 25.0 m above water with an initial speed of 20.0 m/s strikes the water with a final speed of 31.1 m/s, independent of the direction thrown

Answer:

It is proved that the final speed is truly 31.1 m/s

Explanation:

From energy - conservation principle;

E_i = Initial potential energy + Initial Kinetic Energy

Or

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Similarly, for final energy

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So, expressing the formulas for potential and kinetic energies, we now have;

E_i = (m × g × y_i) + (½ × m × v_i²)

Similarly,

E_f = (m × g × y_f) + (½ × m × v_f²)

We are given;

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y_f = 0 m

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v_f = 31.1 m/s

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E_i = m((9.8 × 25) + (½ × 20²))

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E_f = m((9.8 × 0) + (½ × v_f²)

E_f ≈ ½m•v_f²

From energy conservation principle, E_i = E_f.

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485m = ½m•v_f²

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½v_f² = 485

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Answer:

Nanotechnology means working with materials at the scale of one billionth of a metre.

Explanation:

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irina1246 [14]

(BELOW YOU CAN FIND ATTACHED THE IMAGE OF THE SITUATION)

Answer:

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Explanation:

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