US

Which statement is TRUE about the factors affecting physical fitness?A.

seropon [69]

Answer:

D

Explanation:

6 0

2 years ago

(d) If η = 40% and TH = 427°C, what is TC, in °C?

Brrunno [24]

Answer:

$T_C=256.2^{\circ}C$

Explanation:

Given that,

Efficiency of heat engine, $\eta=40\%=0.4$

Temperature of hot source, $T_H=427^{\circ}C$

We need to find the temperature of cold sink i.e. $T_C$ . The efficiency of heat engine is given by :

$\eta=1-\dfrac{T_C}{T_H}$

$T_C=(1-\eta)T_H$

$T_C=(1-0.4)\times 427$

$T_C=256.2^{\circ}C$

So, the temperature of the cold sink is 256.2°C. Hence, this is the required solution.

3 0

3 years ago

The friends take a few minutes to discuss their ideas. Which of Amy's comments with respect to a charged particle moving in a ma

Marizza181 [45]

Answer:

The statement "if the magnetic force is always perpendicular to the velocity, the path of the particle is a straight line" is false.

Explanation:

The equation for the magnetic force on a charge q moving at velocity v on a magnetic field B is given by the (vectorial) Lorentz Force Law $F=qv\times B$

From it we can clearly see that the magnitude of the magnetic force exerted on the particle is proportional to the magnitude of the charge q and to the speed v of the particle, and that it is also perpendicular to the particle's velocity. This means that at each instant it moves perpendicularly to the force, so the work done by the magnetic force on the particle is zero.

The statement "if the magnetic force is always perpendicular to the velocity, the path of the particle is a straight line" is false not only for this but for any force, a force always perpendicular to a velocity will curve the trajectory.

7 0

2 years ago

A student sits on a pivoted stool while holding a pair of weights. The stool is free to rotate about a vertical axis with neglig

Blababa [14]

Answer:

Please Mark As Brainliest!!

a) 4.99 rad/sec b) 6.24 rad/sec c) 7.03 J

Explanation:

a) If the student completes one turn in 1.26 sec, this is called the period of the movement.

If we take into account that the angle rotated during one turn is 2π rads, by definition of angular velocity, we can get this value as follows:

ω = Δθ / Δt = 2*π rad / 1.26 seg = 4.99 rad/sec.

b) As no external torques are acting on the system, the total angular momentum must be conserved, so we can write the following equation:

Li = Lf ⇒ I₁ * ω₁ = I₂* ω₂

So, we can solve for ω₂, as follows:

ω₂ = (I₁ * ω₁) / I₂ = 6.24 rad/sec

c) Appying the work-energy theorem, we know that the work done by the student, must be equal to the change in the kinetic energy, which in this case is only rotational, so we can write:

W = 1/2 I₂* ω₂² - 1/2 I₁ ω₁²

W =1/2 ((2.25 kg.m² * (6.24)²) (rad/sec)² - (1.8 kg.m²* (4.99)²) (rad/sec)²)

W = 7.03 J

4 0

2 years ago

Calculate the kinetic energy of a 64.g bullet moving at a speed of 411.ms . Round your answer to 2 significant digits.

Mandarinka [93]

Answer:

The kinetic energy of the bullet is 5.4 × 10³ J

Explanation:

Hi there!

The equation of kinetic energy is the following:

KE = 1/2 · m · v²

Where:

KE = kinetic energy.

m = mass of the bullet.

v = speed of the bullet.

Let´s convert the mass unit to kg so that our result is in Joules:

64 g · ( 1 kg / 1000 g) = 0.064 kg

Then, the kinetic energy will be the following:

KE = 1/2 · 0.064 kg · (411 m/s)²

KE = 5.4 × 10³ J

8 0

2 years ago