It takes 6400 years for one gram of radium to decay away to only 1/16 (one-sixteenth) of a gram. The half-life of radium is

A car driver traveling at a speed of 108km per hour ,sees a traffic light and stopped after travelling for 20seconds .Find the a

navik [9.2K]

Answer:

– 2.5 m/s²

Explanation:

We have,

• Initial velocity, u = 180 km/h = 50 m/s

• Final velocity, v = 0 m/s (it stops)

• Time taken, t = 20 seconds

We have to find acceleration, a.

$\longrightarrow$ a = (v ― u)/t

$\longrightarrow$ a = (0 – 50)/20 m/s²

$\longrightarrow$ a = –50/20 m/s²

$\longrightarrow$ a = – 5/2 m/s²

$\longrightarrow$ a = – 2.5 m/s² (Velocity is decreasing) [Answer]

6 0

3 years ago

I need help on number 2 and 3

irinina [24]

For 2 draw the molucules very close together. because in soilds the molucules are VERY close to gether.

and for 3 Draw them with a lot of space apart from each other. Molucules move freely and openly in air and space.

Hope this helps! Please mark as brainliest! Thanks!! :D

4 0

4 years ago

Suppose that a wind is blowing in the direction S45°E at a speed of 30 km/h. A pilot is steering a plane in the direction N60°E

Kay [80]

Answer:

The true course: $40.29^\circ$ north of east

The ground speed of the plane: 96.68 m/s

Explanation:

Given:

$V_w$ = velocity of wind = $30\ km/h\ S45^\circ E = (30\cos 45^\circ\ \hat{i}-30\sin 45^\circ\ \hat{j})\ km/h = (21.21\ \hat{i}-21.21\ \hat{j})\ km/h$

$V_p$ = velocity of plane in still air = $100\ km/h\ N60^\circ E = (100\cos 60^\circ\ \hat{i}+100\sin 60^\circ\ \hat{j})\ km/h = (50\ \hat{i}+86.60\ \hat{j})\ km/h$

Assume:

$V_r$ = resultant velocity of the plane

$\theta$ = direction of the plane with the east

Since the resultant is the vector addition of all the vectors. So, the resultant velocity of the plane will be the vector sum of the wind velocity and the plane velocity in still air.

$\therefore V_r = V_p+V_w\\\Rightarrow V_r = (50\ \hat{i}+86.60\ \hat{j})\ km/h+(21.21\ \hat{i}-21.21\ \hat{j})\ km/h\\\Rightarrow V_r = (71.21\ \hat{i}+65.39\ \hat{j})\ km/h$

Let us find the direction of this resultant velocity with respect to east direction:

$\theta = \tan^{-1}(\dfrac{65.39}{71.21})\\\Rightarrow \theta = 40.29^\circ$

This means the the true course of the plane is in the direction of $40.29^\circ$ north of east.

The ground speed will be the magnitude of the resultant velocity of the plane.

$\therefore Magnitude = \sqrt{71.21^2+65.39^2} = 96.68\ km/h$

Hence, the ground speed of the plane is 96.68 km/h.

5 0

3 years ago

What is kelvin scale?

Darina [25.2K]

<span>a scale of temperature with absolute zero as zero, and the triple point of water as exactly 273.16 degrees.</span>

4 0

4 years ago

Read 2 more answers

Which best describes the direction of heat?

Gekata [30.6K]

Answer:

MRCORRECT has answered the question

Explanation:

According to second law of thermodynamic,heat flows from higher to lower temperature region. Heat is the transfer of energy from an object at higher temperature to an object at a lower temperature. so energy flows from warmer to colder objects

6 0

3 years ago