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Elden [556K]
4 years ago
15

If the net work done on an object is zero, what can you determine about the object's kinetic energy?(A) The object's kinetic ene

rgy remains the same.(B) The object's kinetic energy is decreasing.(C) The object's kinetic energy is increasing.(D) The object's kinetic energy is zero.
Physics
1 answer:
aev [14]4 years ago
7 0

Answer:

(D) The object's kinetic energy is zero.

Explanation:

Work theory

Work (W) is defined as the product of force F) by the distance (d)the body travels due to this force:

W= F*d Formula ( 1)

The component of the force that performs work must be parallel to the displacement.

Kinetic Energy Theory

Kinetic energy is the energy associated with bodies that are in motion, depends on the mass and speed of the body.

Ek =(1/2)*m*v²

The kinetic energy, Ek, is measured in joules (J), the mass, m, is measured in kilograms (kg) and the velocity, v, in meters / second (m / s).

Relationship between work and kinetic energy

A body remains at rest if the force applied is zero or if it does not move. In both cases the work will be zero.

For work and kinetic energy to have a non-zero value, the body must be in motion.

In other words, the work is equal to zero if there is no displacement, so its speed will be zero, the same as its kinetic energy.

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A ball is thrown nearly vertically upward from a point near the cornice of a tall building. It just misses the cornice on the wa
vovangra [49]

Answer:

a) 48.5 ft/s

b) 36.5 ft

c) -80.3 ft/s

Explanation:

a)

The equation of motion of the ball is :

y(t) = -16.1 ft/s^2 * t^2 + Vo*t

Where Vo is the initial velocity

If y(5s) = - 160 ft:

-160 ft = -16.1 ft/s^2 * (5 s)^2 + Vo*(5s)

Solving for Vo

Vo  = (16.1*25- 160) ft / 5s = 48.5 ft/s

b)

To answer this question we must first know when the velocity became zero, at this time is when the ball was at its highest point.

v(t) = -32.2 ft/s^2 * t + Vo

t = Vo/32.2ft/s^2 = 1.5 s

And now, the highest point which the ball reached is given by:

y(1.5s) = -16.1 ft/s^2 * (1.5)^2 + Vo*(1.5s)

y(1.5s) = 36.52 ft

c)

We now need the time at which y(t') = -64 ft

-64 = -16.1*t'^2 + 48.5*t'

By means of the quadratic formula, we find that

t' = 4.00498 s ≈ 4 s

And the velocity at t = 4s is:

v(4s) = -32.2 ft/s^2 * 4s +48.5 ft/s = -80.3 ft/s

3 0
4 years ago
The acceleration due to gravity on Mars is 3.60 m/s2. if this is measured at a distance of 3.4 x 10^6 m from the center of the p
densk [106]

As we know that acceleration due to gravity is given by

g = \frac{GM}{r^2}

here we know that

g = 3.60 m/s^2

M = ?

r = 3.4 \times 10^6 m

now we have

3.60 m/s^2 = \frac{(6.67 \times 10^{-11} Nm^2/kg^2)(M)}{(3.4 \times 10^6)^2m^2}

M = 6.24 \times 10^{23} kg

so above is the mass of Mars

8 0
3 years ago
A force F = (2.75 N)i + (7.50 N)j + (6.75 N)k acts on a 2.00 kg mobile object that moves from an initial position of d = (2.75 m
Natasha2012 [34]

Answer:

The work done on the object by the force in the 5.60 s interval is 40.93 J.

Explanation:

Given that,

Force F=(2.75\ N)i+(7.50\ N)j+(6.75\ N)k

Mass of object = 2.00 kg

Initial position d=(2.75)i-(2.00)j+(5.00)k

Final position d=-(5.00)i+(4.50)j+(7.00)k

Time = 4.00 sec

We need to calculate the work done on the object by the force in the 5.60 s interval.

Using formula of work done

W=F\cdot d

W=F\cdot(d_{f}-d_{i})

Put the value into the formula

W=(2.75)i+(7.50)j+(6.75)k\cdot (-(5.00)i+(4.50)j+(7.00)k-(2.75)i+(2.00)j-(5.00)k)

W=(2.75)i+(7.50)j+(6.75)k\cdot((-7.75)i+6.50j+2.00k)

W=2.75\times-7.75+7.50\times6.50+6.75\times2.00

W=40.93\ J

Hence, The work done on the object by the force in the 5.60 s interval is 40.93 J.

4 0
3 years ago
A 60kg student is sitting in a chair and is not moving. what is the force of a student acting on the chair? what is the force of
vazorg [7]

The force with which the student is acting in the chair and the force of the chair acting on the student is 588 N

Explanation:

  • There are two kinds of forces acting on you when you are sitting on the chair, they are the gravitational force and the force exerted by the chair on you.
  • The forces acting on the chair when you are sitting are the gravitational force and the force exerted by you.
  • As per  Newton's third law of motion, for every action, there is an equal and opposite reaction.
  • Hence, F = ma

        that is, F = 60 * 9.8

                       =588 N

  • So, 588 N force should be applied from both sides then only you can sit properly in the chair.
7 0
3 years ago
A baseball is hit so that it travels straight upward after being struck by the bat. A fan observes that it takes 2.90 seconds fo
Natasha_Volkova [10]
We'll assume that the whole scene takes place on Earth.
So the acceleration of gravity is 9.8 m/s² downward.

a).  Gravity makes anything fall 9.8 m/s faster every second.
That's the same thing as rising 9.8 m/s slower every second.

If it takes 2.9 seconds to reach its maximum height, then
it must have started out rising at (9.8 x 2.9) = 28.4 m/s.

b).  The ball left the bat at 28.4 m/s.
After 2.9 seconds, its speed was zero. (That's why it started falling.)
It's average speed during the climb was

                 1/2 (28.4 + 0)  =  14.2 m/s .

It rose straight up at an average speed of 14.2 m/s for 2.9 seconds,
so it reached a maximum  height of

                 (14.2 x 2.9)  =   41.2 meters    .   
4 0
3 years ago
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