How many calories would you take in if you ate the whole box of crackers in one sitting ?

A 2.0 kg book is lying on a 0.78 m -high table. You pick it up and place it on a bookshelf 2.1 m above the floor.Part ADuring th

zloy xaker [14]

Given data:

* The mass of the book is 2 kg.

* The initial height of the book is 0.78 m.

* The final height of the book is 2.1 m.

Solution:

(A). The work done by the gravity on the book is,

$W=mg(h_f-h_i)$

where m is the mass, g is the acceleration due to gravity, h_i is the initial height and h_f is the final height,

The work is done in moving the object in upward direction where as the gravitational force is acting in the down ward direction. Thus, the value g (acceleration due to gravity) is taken as negative in this case.

Substituting the known values,

$\begin{gathered} W=2\times(-9.8)\times(2.1-0.78) \\ W=-19.6\times1.32 \\ W=-25.9\text{ J} \end{gathered}$

Thus, the work done by the gravitational force is -25.9 J.

(B). The work done by the hand on the moving the book is,

$\begin{gathered} W_1=-W \\ =25.9\text{ J} \end{gathered}$

Thus, the work done by the hand on the book is 25.9 J.

7 0

9 months ago

An electron in a TV picture tube is accelerated through a potential difference of 10 kV before it hits the screen. What is the k

laiz [17]

Answer:

10,000 eV

Explanation:

According to the law of conservation of energy, the kinetic energy gained by the electron is equal to its change in electric potential energy:

$K=\Delta U=q \Delta V$

where:

K is the kinetic energy of the electron

$q=1 e$ is the magnitude of the charge of the electron

$\Delta V$ is the potential difference through which the electron has been accelerated

For this electron in the TV, we have

$\Delta V=10 kV=10000 V$

Therefore, the kinetic energy of the electron in electronvolts is

$K=(1 e)(10000 V)=10000 eV$

7 0

3 years ago

An object with a mass of 5.0 kg is accelerating toward the surface of Earth at a rate of 9.8 m/s^2

vlabodo [156]

The answer is A. Force is equal to mass x acceleration. The acceleration due to gravity is a constant so multiplying the mass by 2 would double the force.

4 0

3 years ago

Mary starts at the edge of a circular platform that is slowly rotating on a frictionless axle. She then walks towards the opposi

bulgar [2K]

Answer:

Explanation:

The motion of Mary along the circular path is a centripetal.

As Mary moves from one edge of the circular platform to the other edge, she is covering a distance which is the radius of the circular path at a velocity.

According to the relationship

w = v/r where

w is the angular velocity

r is the radius

v is the linear velocity

Initially, before Mary starts, her linear speed is zero and her angular velocity is also zero. As she move towards the opposite edge, she is covering a distance of radius r. According to the formula, increase in radius will leads to decrease in her angular velocity and vice versa. As Mary starts moving towards the centre of the circular path, her angular velocity increases, at the centre of the platform, her angular velocity is at maximum at this point. As she moves further from the center to the other edge, her angular velocity decreases due to increase in distance covered across the circular path.

6 0

3 years ago

A driver in a car traveling at a speed of 21.8m/s sees a cat 101 m away on the road. How long will it take for the car to accele

kobusy [5.1K]

The acceleration of the car will be needed in order to calculate the time. It is important to consider that the final speed is equal to zero:

$v^2 = v_0^2 + 2ad\ \to\ a = \frac{-v_0^2}{2d} = -\frac{21.8^2\ m^2/s^2}{2\cdot 99\ m} = -2.4\frac{m}{s^2}$

We can clear time in the speed equation:

$v = v_0 + at\ \to\ t = \frac{-v_0}{a} = \frac{-21.8\ m/s}{-2.4\ m/s^2} = \bf 9.08\ s$

If you find some mistake in my English, please tell me know.

3 0

3 years ago

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