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Zina [86]
3 years ago
13

I just need help with these seven!

Physics
1 answer:
Anna [14]3 years ago
5 0
21. light changes its direction when travelling through a new medium because denser mediums have a higher angle of refraction.
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Who makes the first atomic bomb?​
Svetradugi [14.3K]

Answer:

Robert Oppenheimer made the first atomic bomb.

7 0
3 years ago
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Calculate the acceleration of an airplane that starts at rest and reaches a speed 45m/s in 9 seconds
sasho [114]

I believe the acceleration would be 5m/s

All you would need to do is divide the final speed by the time it took to get there. I am only about 80 sure this answer is correct, so take my advise only if you feel comfortable.

3 0
3 years ago
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The half-life of cobalt-60 is 5.26 years. If 50 g are left after 15.8 years, how many
PtichkaEL [24]

Answer:

400 g

Explanation:

The computation of the number of grams in the original sample is shown below:

Given that

half-life = 5.26 years

total time of decay = 15.8 years

final amount = 50.0 g

Now based on the above information  

number of half-lives past is

=  15.8 ÷ 5.26

= 3 half-lives

Now

3 half-lives = 1 ÷ 8 remains = 50.0 g

So, the number of grams would be

= 50.0 g × 8

= 400 g

4 0
2 years ago
Eating 2500 Cal every day a friend of mine maintains a stable weight of 70 kg. One day, after eating 3500 Cal, he decided to do
Kaylis [27]

Answer:

Explanation:

Calories to be burnt = 3500 - 2500 = 1000 Cals .

Efficiency of conversion to mechanical work  is 25 % .

Work needed to burn this much of Cals = 1000 x 100 / 25 = 4000 Cals.

4000 Cals = 4.2 x 4000 = 16800 J  .

Work done in one jump = kinetic energy while jumping

= 1/2 m v²

= .5 x 70 x 3.3²

= 381.15 J .

Number of jumps required = 16800 / 381.15

= 44 .

4 0
2 years ago
A ball that has a mechanical energy of 65 J has 12 J of kinetic energy. The ball has
bulgar [2K]

Answer:

The ball has a potential energy of 53 J.

Explanation:

Mechanical energy, E = Kinetic energy + Potential energy

E = K.E + P.E

65 = 12 + P.E

P.E = 65 – 12

P.E = 53 J

Therefore the potential energy of the ball is 53 J

8 0
3 years ago
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