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3 years ago

A gymnast pushed down on a trampoline during a routine. What is the reaction

Physics

1 answer:

kompoz [17]3 years ago

6 0

Answer:

d) The trampoline pushes back up on the gymnast.

Explanation:

According to Newton's third law of motion; for every action force, there is an equal and opposite reaction force. The action force and reaction force are reciprocal to one another i.e. they act oppositely to one another. The reaction force acts in an opposite direction to the action force and vice versa.

In this question, a gymnast pushed down on a trampoline during a routine. This is called the ACTION FORCE. In conformity to Newton's third law, the trampoline pushes back up on the gymnast. This opposite force is called the REACTION FORCE.

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What is field in physics

Troyanec [42]

Where everything is effected by a force

6 0

3 years ago

An elaborate pulley consists of four identical balls at the ends of spokes extending out from a rotating drum. A box is connecte

Klio2033 [76]

Answer:

its speed will be less than V

Explanation:

When the ball falls a distance d, its final kinetic energy plus rotational kinetic energy of the drum equals its initial potential energy.

K = U

With its speed V at the end of d, we have

1/2mV² + 1/2Iω² = mgd where I = rotational inertia of drum and balls, ω = angular speed of drum and balls and m = mass of box

1/2mV² + 1/2Iω² = mgd

1/2mV² = mgd - 1/2Iω²

V² = [2(mgd - 1/2Iω²)/m]

V = √[2(mgd - 1/2Iω²)/m]

When the four balls are moved inward closer to the drum, their rotational inertia increases and also its angular speed which thus causes an increase in rotational kinetic energy. But, since the box still falls the same distance of d, its final kinetic energy plus rotational kinetic energy of the drum plus balls still equals its initial potential energy

K = U

I' = new rotational inertia of drum and balls, ω' = new angular speed of drum and balls

With its new speed is now V' at the end of d,

1/2mV'² + 1/2I'ω'² = mgd

1/2mV'² = mgd - 1/2I'ω'²

V² = [2(mgd - 1/2I'ω'²)/m]

V' = √[2(mgd - 1/2I'ω'²)/m]

Since I' and ω' increase, the rotational kinetic energy of the drum and balls (1/2I'ω'²) increases. Thus, the difference (mgd - 1/2I'ω'²) < (mgd - 1/2Iω²) which implies that the kinetic energy of the box decreases. Hence, since its kinetic energy decreases, its speed V' also decreases.

So, V' < V

So, its speed will be less than V.

3 0

3 years ago

Sound waves that enter the external acoustic meatus eventually encounter the __________, which then vibrates at the same frequen

7nadin3 [17]

Answer:

tympanic membrane (eardrum)

Explanation:

The sound waves spread through the air and reach the outer ear, into which they penetrate through the ear canal. In doing so, they stimulate the eardrum, which closes the inner end of the duct. By vibrating this membrane, the vibration of a chain of ossicles located in the middle ear is induced. These ossicles transmit their vibration to the oval window, which is a membranous structure that communicates the middle ear with the cochlea of the inner ear. When the oval membrane moves, it moves the liquid (perilymph) that fills one of the three cavities of the cochlea generating waves in it. These waves mechanically stimulate the sensory cells (hair cells) located in the organ of Corti, within the cochlea in the central cavity, the middle ramp. This cavity is filled with a liquid rich in K +, endolymph. The cells embedded in the endolymph, change their permeability to K + due to the movement of the cilia and respond by releasing a neurotransmitter that excites the nerve terminals, which initiate the auditory sensory pathway.

3 0

3 years ago

If we have a velocity of 20 m/s and our acceleration is -5 m/s, then after 2 seconds our velocity will be....

svetoff [14.1K]

Answer:

v = 10 m/s

Explanation:

We have,

Our initial velocity is 20 m/s

Our acceleration, $a=-5\ m/s^2$

It is required to find the velocity after 2 seconds. It is a concept based on equation of kinematics. Using first equation:

$v=u+at$

Plugging all the known values

$v=20+(-5)(2)\\\\v=10\ m/s$

So, our final velocity is 10 m/s.

6 0

4 years ago

The manager of a department store is pushing horizontally with a force of magnitude 200N on a box of shirts. The box is sliding

Andreas93 [3]

Found the missing options on internet:
<span>a) it is less than 200 N; b) it is greater than 200 N; c) it is equal to 200 N; d) none of these statements are necessarily true
</span>
Solution:
The correct answer is a) it is less than 200 N.

In fact, the box is sliding with forward acceleration different from zero. This means that the net force acting on the box is different from zero, because Newton's second law states that:
$\sum F = ma$
the resultant of the forces acting on an object is equal to its mass times its acceleration.

In this case, we have 2 forces acting on the box:
- the force of 200 N of the man pushing the box
- the frictional force, acting against the direction of motion
The net acceleration is forward, this means that the net force acting on the box must be directed forward, therefore the magnitude of the frictional force must be smaller than the force of 200 N that pushes the box.

8 0

3 years ago