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ki77a [65]
3 years ago
14

Given that: = 2i + 9j ; and ⃗ = -i – 4j . Find . ⃗ ​

Physics
1 answer:
Marat540 [252]3 years ago
5 0

Answer:

A.B = -38

Explanation:

A = 2i + 9j and B = -i - 4j.

So, A.B = (2i + 9j).(-i - 4j)

= 2i.(-i) + 2i.(-4j) + 9j.(-i) + 9j.(-4j)

= -2i.i - 8i.j - 9j.i - 36j.j

since i.i = 1, j.j = 1, i.j = 0 and j.i = 0, we have

A.B = -2(1) - 8(0) - 9(0) - 36(1)

A.B = -2 - 0 - 0 - 36

A.B = -38

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What is the height of a building that an object is dropped from if it has a mass of 3 kg and hits the ground with a velocity of
Marizza181 [45]

Answer:

125 m

Explanation:

m = 3kg

v = 50m/s

u = 0m/s

a = +g = 10m/s²

s = H = ?

using the formula,

v² = u² + 2as

50² = 0² + 2(10)(H)

2500 = 20H

H = 2500/20

H = 125m

8 0
2 years ago
Using software, a simulation of a javelin being thrown both on Earth and on the moon is created. In both cases, the velocity and
mario62 [17]

Horizontal distance covered by a projectile is X = Vix *T

where Vix is the initial horizontal component of velocity and T is time taken by the projectile

Vix = ViCos theta

In question they said that initial velocity and angle is same on earth and moon

so Vix would remains same

now let's see about time taken T

time taken to reach the highest point

Vfy = Viy +gt

at highest point vertical velocity become zero so Vfy =0

0 = Vi Sin theta + gt

t = Vi Sintheta /g

Total time taken to land will be twice of that

On earth

Te= 2t

Te = 2Sinθ/g

on moon g is one-sixth of g(earth)

Tm = 2Sinθ/(g/6)

Tm = 6(2Sinθ/g)

Tm = 6Te

so total time taken by the projectile on moon will be six times the time taken on earth

From first equation X = Vix*T

we can see that X will also be 6 times on moon than earth

so projectile will cover 6 times distance on moon than on earth

4 0
2 years ago
Read 2 more answers
PLEASE HURRY, I'M BEING TIMED!
spayn [35]

Option D is correct. The speed at which the earth's surface moves because of the earth's rotation will then be equivalent to -10³ km/hr

Speed is a body is defined as the ratio of the distance with respect to the time taken by the body. Mathematically:

Speed = Distance/Time

GIven the following

Distance = 104km/hr

If it is 6:00 p.m. in New York, it is 7:00 a.m. of the next day of the week in Tokyo, this means that the time difference between New York and Tokyo is 11 hours.

Time = -11 hours

Get the required speed

Speed = 104/-11

Speed = -9.454545

Speed = -10km/hr

The speed at which the earth's surface moves because of the earth's rotation will then be equivalent to -10³ km/hr

Learn more here: brainly.com/question/2583051

4 0
2 years ago
Read 2 more answers
How many meters are in 32 kilometers
lukranit [14]

Answer:

32,000 m

Explanation:

Conversion

1km ===> 1000m

32km===>x

x = (32 × 1000) ÷ 1

5 0
3 years ago
A charge of -5.02 nC is uniformly distributed on a thin square sheet of nonconducting material of edge length 21.8 cm. "What is
Maru [420]

Answer:

A charge of -5.02 nC is uniformly distributed on a thin square sheet of nonconducting material of edge length 21.8 cm. "What is the surface charge density of the sheet"?

Explanation:

Surface charge density is a measure of how much electric charge is accumulated over a surface. It can be calculated as the charge per unit area.

We will convert all parameters in SI units.

Charge = Q = -5.02nC

Q  = -5.02×10^{-9}C

As it is clear from question that Sheet is a square (All sides will be of equal length)

Area = A = (21.8×10^{-2}m) (21.8×10^{-2}m)  = 4.75×10^{-4}m²

A  = 4.75×10^{-4}m²

Surface charge density = Q/A

Surface charge density = (-5.02×10^{-9}C)/(4.75×10^{-4}m²)

Surface charge density = -1.057×10^{-5} Cm^{-2}

3 0
3 years ago
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