Which of the following should a scalar measurement have?

PtichkaEL [24]

Wheel, axel and rope

3 0

3 years ago

A gang of robbers is escaping across city roofs at night. They come to the edge of one building and need to drop down to their g

REY [17]

Answer:

a) They will hit the ground with a speed of 19.6 m/s.

b) They are at a height of 20 m.

c) It is not a safe jump.

Explanation:

Hi there!

a) The equations of height and velocity in function of time of a free falling body are the following:

h = h0 + v0 · t + 1/2 · g · t²

v = v0 + g · t

Where:

h = height of the object at time t.

h0 = initial height.

v0 = initial velocity.

t = time.

g = acceleration due to gravity (-9.8 m/s² considering downward as negative direction).

v = velocity of the object at time t.

Using the equation of velocity, let's find the velocity at which they will hit the ground. The pebble is dropped (initial velocity = 0) and it takes 2 s to reach the ground:

v = v0 + g · t (v0 = 0)

v = g · t

v = -9.8 m/s² · 2.0 s

v = -19.6 m/s

They will hit the ground with a speed of 19.6 m/s.

b)Now, we have to use the equation of height:

h = h0 + v0 · t + 1/2 · g · t²

If we place the origin of the frame of reference on the ground, we have to find the initial height (h0) knowing that at t = 2.0 s, h = 0 m

0 m = h0 - 1/2 · 9.8 m/s² · (2.0 s)²

h0 = 1/2 · 9.8 m/s² · (2.0 s)²

h0 = 20 m

They are at a height of 20 m.

c)According to a NASA paper (Issues on Human Acceleration Tolerance After Long-Duration Space Flights, figure 10), if you fall with a vertical velocity greater than 17 m/s it is unlikely that you will survive. So, it is not a safe jump.

3 0

3 years ago

Two metra trains approach each other on separate but parallel tracks. one has a speed of 90 km/hr, the other 80 km/hr. initially

Gennadij [26K]

The trains take <u>57.4 s</u> to pass each other.

Two trains A and B move towards each other. Let A move along the positive x axis and B along the negative x axis.

therefore,

$v_A=90 km/h\\ v_B=-80 km/h$

The relative velocity of the train A with respect to B is given by,

$v_A_B=v_A-v_B\\ =(90km/h)-(-80km/h)\\ =170km/h$

If the train B is assumed to be at rest, the train A would appear to move towards it with a speed of 170 km/h.

The trains are a distance d = 2.71 km apart.

Since speed is the distance traveled per unit time, the time taken by the trains to cross each other is given by,

$t= \frac{d}{v_A_B}$

Substitute 2.71 km for d and 170 km/h for $v_A_B$

$t= \frac{d}{v_A_B}\\ =\frac{2.71 km}{170 km/h} \\ =0.01594 h$

Express the time in seconds.

$t=(0.01594h)(3600s/h)=57.39s$

Thus, the trains cross each other in <u>57.4 s</u>.

6 0

3 years ago

A ray of light incident in air strikes a rectangular glass block of refractive index 1.5 at angle of incidence of 45.

Gwar [14]

Refraction is said to occur when there is a change in the speed of light.

<h3>What is the angle of refraction?</h3>

We know that refraction is said to occur when there is a change in the speed of light as it travels form one medium to another.

Given that the refractive index of the rectangular glass block is 1.5. The angle of refraction can be obtained by the use of the Snell's law;

n = sin i /sinr

n = refractive index

sini = angle of incidence

sin r = angle of refraction

sinr = sini/n

sinr = sin 45/1.5

= 0.471

r = 28 degrees

b) Now;

sinr =sin 45/1.2

sinr = 0.589

r = 36 degrees

For the glass

sinr = sin 36/1.5

sin r = 0.392

r = 23 degrees

Learn more about angle of refraction:brainly.com/question/2660868

#SPJ1

4 0

2 years ago

A suitcase has a width of 55 cm. Which unit conversation fraction should you use to find the width in inches?

Crank

Answer:

2,54 cm are equal to 1 inch

Explanation:

Doing the conversion:

$55[cm]*\frac{1[inch]}{2,54[cm]} =21,65[inch]$

6 0

3 years ago