A car that increase its speed from 20 km/h to 100 km/h undergoes -------acceleration,

9. Consider the elbow to be flexed at 90 degrees with the forearm parallel to the ground and the upper arm perpendicular to the

mojhsa [17]

Answer:

Moment about SHOULDER ∑ τ = 3.17 N / m,

Moment respect to ELBOW Στ= 2.80 N m

Explanation:

For this exercise we can use Newton's second law relationships for rotational motion

∑ τ = I α

The moment is requested on the elbow and shoulder at the initial instant, just when the movement begins.

They indicate the angular acceleration, for which we must look for the moments of inertia of the elements involved

The mass of the forearm with the included weight is approximately 2.3 kg, with a length of about 50cm

Moment about SHOULDER

∑ τ = I α

I = I_forearm + I_sphere

the forearm can be approximated as a fixed bar at one end

I_forearm = ⅓ m L²

the moment of inertia of the mass in the hand, let's approach as punctual

I_mass = m L²

we substitute

∑ τ = (⅓ m L² + M L²) α

let's calculate

∑ τ = (⅓ 2.3 0.5² + 0.5 0.5²) 10

∑ τ = 3.17 N / m

Moment with respect to ELBOW

In this case, the arm exerts an upward force (muscle) that is about 3 cm from the elbow

Στ = I α

I = I_ forearm + I_mass

I = ⅓ m (L-0.03)² + M (L-0.03)²

let's calculate

i = ⅓ 2.3 0.47² + 0.5 0.47²

I = 0.2798 Kg m²

Στ = 0.2798 10

Στ= 2.80 N m

3 0

3 years ago

A hiker determines the length of a lake by listening for the echo of her shout reflected by a cliff at the far end of the lake.

ArbitrLikvidat [17]

Answer:

L = 499 m

Explanation:

If we assume that the speed of sound is constant, that travels along a straight line, and that the echo is instantaneous, we can find the total distance travelled by the sound, as follows, just applying the definition of average velocity:

$\Delta x = v_{s} * t = 343 m/s* 2.91 s = 998 m$

If we assume that the time needed to reach to the cliff, is the same used for the return travel, the length of the lake will be exactly half of the total distance calculated:

$l_{lake} = \frac{\Delta x}{2} = \frac{998m}{2} = 499 m$

The length of the lake is 499 m.

8 0

3 years ago

An electric field is produced by the very long, uniformly charged rod drawn above. If the strength of the electric field is E1 a

Debora [2.8K]

Answer: hello the complete question is attached below

answer :

r2 = 4r1

Explanation:

Electric field strength = F / q

we will assume the rod has an infinite length

For an infinitely charged rod

E ∝ 1/ r

considering two electric fields E1 and E2 at two different locations as described in the question

E1/E2 = r1/r2 ----- ( 2 )

<u>Calculate for r2 when E2 = E1/4 </u>

back to equation 2

E1 / (E1/4) = r1 / r2

∴ r2 = 4r1

3 0

3 years ago

How does state-dependence impact memory recall?

NNADVOKAT [17]

Answer:

The state of the person under the influence of alcohol

The place in which the memory was initially encoded for the retrieval of information.

Retrieval of information is generally better given similar rather than different contextual cues Motivational and emotional factors

These are also likely to affect recall and forgetting.

Explanation:

7 0

3 years ago

Read 2 more answers

Can someone help me ?

hammer [34]

Answer:

1) Time interval Blue Car Red Car

0 - 2 s Constant Velocity Increasing Velocity

2 - 3 s Constant Velocity Constant Velocity

3 - 5 s Constant Velocity Increasing Velocity

5 - 6 s Constant Velocity Decreasing Velocity

2) For Red and Blue car y₂ = 120 v = $\frac{y_{2}-y_{1}}{t_{2}-t_{1}}$ = $\frac{120-0}{6-0}$ = 20 m/s

We get the same velocity for two cars because it is the average velocity of the car at the given interval of time. It is measured for initial and final position.

3) At t = 2s, the cars are the same position, and are moving at the same rate

Position - same

Velocity - same

The position-time graph shares the same spot for two cars.

4 0

3 years ago