**Answer:**

1.526 m

**Explanation:**

The motion sensor sends sound waves in air which travels at a speed of 343 m per second at 20 degree. If d be the distance of the reflecting object

total distance travelled = 2d

Time taken t = 8.9 x 10⁻³ s

velocity v = 2d / t

343 = 2 d / (8.9 x 10⁻³)

d = 1.526 m

**Answer:**

**200N**

**Explanation:**

Given parameters:

Mass of wagon = 100kg

Acceleration = 2m/s²

Unknown:

Force on the wagon = ?

Solution:

From Newton's second law of motion:

Force = mass x acceleration

Now insert the parameters and solve;

Force = 100 x 2 = **200N**

**Answer:**

These electrons are "**bonding pairs**."

**Explanation:**

Two atoms share a pair of two valence electrons between them to form a covalent bond. (Of course they can share more than one pairs to produce a double, or a triple bond.) These valence electrons are called "bonding pairs."

In contrast, if a pair of valence electrons on an atom are not shared with another atom, that pair of valence electrons is called a "lone pair".