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Sonja [21]
3 years ago
15

A person lifts a 4.5 kg cement block a vertical distance of 1.2 m and then carries the block horizontal- ly a distance of 7.3 m.

determine the work done by the person and by the force of gravity in this process.
Physics
1 answer:
Delvig [45]3 years ago
6 0
<span>When a person lifts the block, the block has more potential energy. Therefore the person does positive work on the block. work = m g h work = (4.5 kg) (9.80 m/s^2) (1.2 m) work = 52.92 joules The person's work on the block is 52.92 joules When the block is being raised, the force of gravity opposes the motion. Therefore the force of gravity does negative work on the block. work = - (force) (h) work = - m g h work = -(4.5 kg) (9.80 m/s^2) (1.2 m) work = -52.92 joules The work done by the force of gravity on the block is -52.92 joules Note that when the block is moved horizontally, the potential energy does not change. Therefore there is no work done on the block when it moves horizontally (we are assuming that the kinetic energy does not change).</span>
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14. Three identical light bulbs are connected in series, then are disconnected and arranged in parallel. For each of the scenari
Inessa [10]
In order to make things easier to describe and explain, let's call
the resistance of each bulb 'R', and the battery voltage 'V'.

a).  In series, the total resistance is 3R.
In parallel, the total resistance is R/3.
Changing from series to parallel, the total resistance of the circuit
decreases to 1/9 of its original value.

b).  In series, the total current is  V / (3R) .
In parallel, the total current is  3V / R .
Changing from series to parallel, the total current in the circuit
increases to 9 times its original value.

c).  In series, the power dissipated by the circuit is 

                                   (V) · V/3R  =  V² / 3R .

In parallel, the power dissipated by the circuit is

                                   (V) · 3V/R  =  3V² / R .

Changing from series to parallel, the power dissipated by
the circuit (also the power delivered by the battery) increases
to 9 times its original value.

8 0
3 years ago
A 3.0 kg object moving 8.0 m/s in the positive x direction has a one-dimensional elastic collision with an object (mass = M) ini
finlep [7]
<h2>Option 2 is the correct answer.</h2>

Explanation:

Elastic collision means kinetic energy and momentum are conserved.

Let the mass of object be m and M.

Initial velocity object 1 be u₁,  object 2 be u₂

Final velocity object 1 be v₁,  object 2 be v₂

Initial momentum = m x u₁ + M x u₂ = 3 x 8 + M x 0 = 24 kgm/s

Final momentum = m x v₁ + M x v₂ = 3 x v₁ + M x 6 = 3v₁ + 6M

Initial kinetic energy = 0.5 m x u₁² + 0.5 M x u₂² = 0.5 x 3 x 8² + 0.5 x M x 0² = 96 J

Final kinetic energy = 0.5 m x v₁² + 0.5 M x v₂² = 0.5 x 3 x v₁² + 0.5 x M x 6² = 1.5 v₁² + 18 M

We have

            Initial momentum = Final momentum

            24 = 3v₁ + 6M

            v₁ + 2M = 8

             v₁ = 8 - 2M

            Initial kinetic energy = Final kinetic energy

            96 = 1.5 v₁² + 18 M

            v₁² + 12 M = 64

Substituting  v₁ = 8 - 2M

           (8 - 2M)² + 12 M = 64    

           64 - 32M + 4M² + 12 M = 64    

            4M² = 20 M

               M = 5 kg

Option 2 is the correct answer.  

6 0
3 years ago
ECONOMICS !!!!
gulaghasi [49]

Answer:

B

Explanation:

Absolute advantage is the capability of a commercial entity to produce goods using fewer resources compared to rivals. Using the same inputs, an entity with an absolute advantage produces a larger output compared to competitors. It means the firm has a lower marginal cost of production. Therefore, its products will have the lowest prices in the market.  

6 0
2 years ago
The key idea of the transformation called translation is the gliding or sliding of every point in the plane the same direction.
Mrrafil [7]
That statement is true.

There are several definitions about transformation called translation, but the key idea is the gliding or sliding of every point in the plane the same direction.

Hope this helps
6 0
3 years ago
Read 2 more answers
An egg is thrown upward with a velocity of 4.5 m/s. How long will it take to reach it's maximum height?
Ray Of Light [21]

Answer:

0.45 seconds

Explanation:

Letting the value of g = 10 m/s/s

final velocity (v) = 0 m/s (since the egg will come to rest at the maximum height)

initial velocity(u) = 4.5 m/s

acceleration = -10 m/s/s (since the gravity is acting against the egg)

time = t seconds

From the first equation of motion:

<em>v = u + at</em>

<em>0 = 4.5 + (-10)t</em>

<em>t = -4.5 / -10</em>

t = 0.45 seconds

3 0
3 years ago
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