Which of the following is an example of static friction?

Mode of physical activity <br> A.frequency <br> B.intensity <br> C.time <br> D.type

Artyom0805 [142]

A.frequency

That's the answer

6 0

3 years ago

In a mixture of the gases oxygen and helium, which statement is valid: (a) the helium molecules will be moving faster than the o

mixer [17]

Answer:

a

Explanation:

Given:

In a mixture of the gases oxygen and helium, which statement is valid:

(a) the helium molecules will be moving faster than the oxygen molecules, on average

(b) both kinds of molecules will be moving at the same speed

(c) the oxygen molecules will, on average, be moving more rapidly than the helium molecules

(d) the kinetic energy of the helium will exceed that of the oxygen

(e) none of the above

Solution:

- We will use Boltzmann distribution to answer this question. The root mean square speed of molecules of a gas gives the average speed as follows:

V_rms = sqrt ( 3 k T / m )

- Where, k is the Boltzmann constant, T is the temperature and m is the mass of a single molecule of a gas.

- In general, a mixture has a constant equilibrium temperature T_eq.

- So the v_rms is governed by the mass of a single molecule.

- We know that mass of single molecule of Oxygen is higher than that of Helium molecule. Hence, the relation of mass is inversely proportional to square of root mean speed. So the helium molecules will be moving faster than the oxygen molecules.

- Note: The kinetic energy of the mixture remains constant because it is due to the interaction of the molecules within i.e oxygen and helium. Which makes the kinetic energy independent of mass.

E_k = 0.5*m*v_rms^2

E_k = 0.5*m*(3*k*T/ m )

E_k = 0.5*3*k*T

Hence, E_k is only the function of Temperature which we already established to remain constant at equilibrium.

8 0

3 years ago

Consider this situation: A baseball player dives head-first

siniylev [52]

Of the forces listed I think the force of him diving and sliding across the infield acted on the player.

I think so because the slowing down was a result of an action, and I don’t think that should count as An action when it is the result of an action. However, the act of diving head-first into second base and sliding across the infield are independent actions and will cause friction, which will act upon the player.

7 0

2 years ago

What is the speed of an object after falling (from rest) a distance of 9.80 meters near the surface of the Earth? Assume air

madam [21]

Hi there!

We can use the kinematic equation:

$v_f^2 = v_i^2 + 2ad$

vf = Final velocity (? m/s)

vi = initial velocity (0 m/s, dropped from rest)

a = acceleration (due to gravity, 9.8 m/s²)

d = distance (9.8 m)

Simplify the equation to solve for vf:

$v_f^2 = 0 + 2ad\\\\v_f = \sqrt{2ad}$

Substitute in the given values:

$v_f = \sqrt{2(9.8)(9.8)} = \boxed{13.86 m/s}$

8 0

2 years ago

PLEASE HELP! 2ND TIME I ASKED THIS!!!

Goshia [24]

The train is moving at 50 m/s and Emma is walking down the aisle with 1 m/s speed in the same direction of train. The relative velocity of Emma with respect to other passengers pf the train would be 1 m/s. This is because, the train is not moving relative to them and only emma is moving at 1 m/s. If a person observes from outside, Emma would have (50 +1) m/s = 51 m/s velocity.

relative velocity when two objects are moving in same direction as oberved from outside observer:

$v_{ab}=v_a+v_b$

relative velocity when two objects are moving in the opposite directionas oberved from outside observer:

$v_{ab}=v_a-v_b$

4 0

3 years ago