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Katena32 [7]
3 years ago
8

A force F acts on an object undergoing a displacement s, the force being oriented at an angle θ with respect to the displacement

. Which one of the following correctly describes ALL of the circumstances under which the work done by the force is zero? Entry field with incorrect answer a) The displacement is zero, or the angle is 90°. b) The force is zero, or the displacement is zero, or the angle is 90°. c) The force is zero, or the angle is 90°. d) The force is zero, or the displacement is zero, or the angle is 180°. e) The force is zero, or the displacement is zero.
Physics
1 answer:
olasank [31]3 years ago
7 0

Answer:

b) The force is zero, or the displacement is zero, or the angle is 90°.

Explanation:

The work done by a force F, acting on an object undergoing a displacement s, is given by:

W=Fscos\theta

\theta is the angle between the force and the displacement. Thus, the work is zero, when the force is zero, or the displacement is zero, or the angle is 90°, since the cosine of this angle is zero.

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A 2.0 kg, 20-cm-diameter turntable rotates at 100 rpm ons tionless bearings. Two 500 g blocks fall from above, hit the tum ble s
Verdich [7]

There are mistakes in the question.The correct question is here

A 2.0 kg, 20-cm-diameter turntable rotates at 100 rpm on frictionless bearings. Two 500 g blocks fall from above, hit the turntable simultaneously at opposite ends of a diameter, and stick. What is the turntable’s angular velocity, in rpm, just after this event?

Answer:

w=50 rpm

Explanation:

Given data

The mass turntable M=2kg

Diameter of the turntable d=20 cm=0.2 m

Angular velocity ω=100 rpm= 100×(2π/60) =10.47 rad/s

Two blocks Mass m=500 g=0.5 kg

To find

Turntable angular velocity

Solution

We can find the angular velocity of the turntable as follow

Lets consider turntable to be disk shape and the blocks to be small as compared to turntable

I_{turntable}w=I_{block1}w^{i}+I_{turntable}w^{i}+I_{block2}w^{i}

where I is moment of inertia

w^{i}=\frac{I_{turntable}w}{I_{block1}w^{i}+I_{block2}w^{i}+I_{turntable}w^{i}}\\   So\\I_{turntable}=M\frac{r^{2} }{2}\\I_{turntable}=2*(\frac{(0.2/2)}{2} )\\ I_{turntable}=0.01 \\And\\I_{block1}=I_{block2}=mr^{2}\\I_{block1}=I_{block2}=(0.5)*(0.2/2)^{2} \\ I_{block1}=I_{block2}==0.005\\so\\w^{i}=\frac{I_{turntable}w}{I_{block1}w^{i}+I_{block2}w^{i}+I_{turntable}w^{i}}\\w^{i}=\frac{0.01*(10.47)}{0.005+0.005+0.01} \\w^{i}=5.235 rad/s\\w^{i}=5.235*(60/2\pi )\\w^{i}=50 rpm

7 0
3 years ago
A bird has a kinetic energy of 3 J and a potential energy of 25 J. What is the mechanical energy of the bird?
Ahat [919]

Answer:

28 J

Explanation:

Mechanical energy is the sum of kinetic and potential energy in an object that is used to do work. In other words, it is energy in an object due to its motion or position, or both.

In physics, mechanical energy (Emech) is the energy associated with the motion and position of an object usually in some force field.

Therefore:

ME = KE + PE = 25 + 3 = 28 J

8 0
3 years ago
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Which formation moves sediment and erodes rock?
borishaifa [10]

Answer:

C

Explanation:

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3 years ago
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A closely wound rectangular coil of 80 turns has dimensions 25.0 \rm cm by 40.0 \rm cm. The plane of the coil is rotated from a
Pepsi [2]

Answer:

88.3

Explanation:

Emf in a rotating coil is given by rate of change of flux:

E= dФ/dt=(NABcos∅)/ dt

N: number of turns in the coil= 80

A: area of the coil= 0.25×0.40= 0.1

B: magnetic field strength= 1.1

Ф: angle of rotation= 90- 37= 53

dt= 0.06s

E= (80 × 0.4× 0.25×1.10 × cos53)/0.06= 88.3V

4 0
3 years ago
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Gravity pulled materials together forming the planets in our solar system. The inner planets consist of dense material, such as
Ede4ka [16]

Scientist identify the process in which gravity pulled materials together forming the planets in our solar system as accretion.

Accretion is the formation model of planets in our solar system in which gravity pulls materials together forming the planets.

This formation model accounts for the formation of the inner planets made of of dense material such as iron. These planets include Mercury, venus, earth etc.

As the gravity pulls in the more dense material, the less dense material such as ice, liquid and gas colect together to form the outer planets, which include Jupiter, Uranus, etc.

So, Scientist identify the process in which gravity pulled materials together forming the planets in our solar system as accretion.

Learn more about accretion here:

brainly.com/question/17392929

7 0
3 years ago
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