Slow twitch muscles are needed for?

A pole-vaulter is nearly motionless as he clears the bar, set 4.2 m above the ground. He then falls onto a thick pad. The top of

Inessa05 [86]

initial height of the pole vaulter = 4.2 m

height of the pole vaulter just before it touch the pad = 80 cm

so the total displacement of pole vaulter just before he will touch the pad = 4.2 - 0.80 = 3.4 m

now by kinematics

$v_f^2 - v_i^2 = 2a d$

$v_f^2 - 0^2 - 2* 9.8*3.4$

$v_f^2 = 66.64$

$v_f = 8.16 m/s$

now after this he will come to rest after compressing the pad by 50 cm

so again we can use kinematics to find its acceleration

$v_f^2 - v_i^2 = 2 a d$

$0 - 8.16^2 = 2*a*0.50$

$a = -66.64 m/s^2$

so here its acceleration will be - 66.64 m/s^2

4 0

3 years ago

How often do very active sunspot and solar flare cycles take place?

alexira [117]

11 Years

Usually sunspot and solar flare cycles vary. But the average duration occurs every 11 years, sometimes 9-14 years as well.

3 0

3 years ago

Read 2 more answers

A spring with spring constant 15.5 N/m hangs from the ceiling. A ball is suspended from the spring and allowed to come to rest.

Aloiza [94]

Answer:

A) 138.8g

B)73.97 cm/s

Explanation:

K = 15.5 Kn/m

A = 7 cm

N = 37 oscillations

tn = 20 seconds

A) In harmonic motion, we know that;

ω² = k/m and m = k/ω²

Also, angular frequency (ω) = 2π/T

Now, T is the time it takes to complete one oscillation.

So from the question, we can calculate T as;

T = 22/37.

Thus ;

ω = 2π/(22/37) = 10.5672

So,mass of ball (m) = k/ω² = 15.5/10.5672² = 0.1388kg or 138.8g

B) In simple harmonic motion, velocity is given as;

v(t) = vmax Sin (ωt + Φ)

It is from the derivative of;

v(t) = -Aω Sin (ωt + Φ)

So comparing the two equations of v(t), we can see that ;

vmax = Aω

Vmax = 7 x 10.5672 = 73.97 cm/s

6 0

3 years ago

If a polythene rod is rubbed with a dry cloth, what kind of charge would it gain? A) positive, due to extra protons. B) positive

Likurg_2 [28]

Answer:

D) negative, due to extra electrons.

Explanation:

The charge that would be gained will be negative charges due to extra electrons.

Electrons are usually lost or gained by bodies that comes in contact with one another.

They occupy the orbital space in an atom and are not strongly held by forces within the atom.

Protons cannot be lost in such manner. They occupy the nucleus and are bounded by strong chemical forces within it.

The polythene and rods are both made up of chemical substances whose units called atoms are made up of subatomic particles of protons, neutrons and electrons. As with all kinds of matter, there would be pool of free electrons round them that can easily be rubbed off due to the weak attractive forces binding them in the atomic sphere.

When the polythene and rods are rubbed, there would be a loss of electrons and the gaining body, polythene becomes negatively charged.

6 0

3 years ago

An object of mass 2kg is on an incline where there is an applied force of 15N. The

seraphim [82]

a) See free-body diagram in attachment

b) The acceleration is $2.46 m/s^2$

Explanation:

a)

The free-body diagram of an object is a diagram representing all the forces acting on the object. Each force is represented by a vector of length proportional to the magnitude of the force, pointing in the same direction as the force.

The free-body diagram for this object is shown in the figure in attachment.

There are three forces acting on the object:

The weight of the object, labelled as $mg$ (where m is the mass of the object and g is the acceleration of gravity), acting downward
The applied force, $F_a$ , acting up along the plane
The force of friction, $F_f$ , acting down along the plane

b)

In order to find the acceleration of the object, we need to write the equation of the forces acting along the direction parallel to the incline. We have:

$F_a - F_f - mg sin \theta = ma$