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3 years ago

Which vector should be negative?

Physics

1 answer:

Bas_tet [7]3 years ago

5 0

The velocity of a falling object. In physics, down is regarded as a negative direction.

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An acorn with a mass of 0.300 kilograms falls from a tree. What is its kinetic energy when it reaches a velocity of 5.oo m/s?

vladimir1956 [14]

Answer: 3.75 joules

Explanation:

Given that:

Mass of acorn = 0.300 kilograms

velocity = 5.oo m/s

Kinetic energy = ?

Since, kinetic energy is the energy possessed by a moving object, its value depends on the mass M and velocity V of the acorn.

Thus, Kinetic energy = 1/2 x mv^2

= 1/2 x 0.300kg x (5.00m/s)^2

= 0.5 x 0.3kg x (5.00m/s)^2

= 0.15 x (5.00m/s)^2

= 3.75 joules

Thus, the kinetic energy of the falling acorn is 3.75 joules

5 0

3 years ago

It takes you 9.8 min to walk with an average velocity of 1.9 m/s to the north from the bus stop to the museum entrance.

Dahasolnce [82]

60 x 9.8 = 588
588 x 1.9 = 1117.2

5 0

3 years ago

A motorcycle of mass 100 kilograms slowly rolls off the edge of a cliff and falls for three seconds before reaching the bottom o

Jet001 [13]

Answer:

C) 3,000 kg m/s

Explanation:

We can consider the horizontal velocity of the motorcycle to be zero, since it rolls off the edge of the cliff very slowly. So, we only need to find the vertical velocity at the time of the impact with the ground.

The vertical velocity of the motorcycle at time t is given by (free-fall motion):

$v(t)=v_0 -gt$

where

$v_0=0$ is the initial vertical velocity (zero, since the motorcycle is not moving)

g = 9.8 m/s^2 is the acceleration due to gravity

t is the time

Since the motorcycle hits the ground after t = 3 seconds, we have

$v(3 s)=0-(9.8 m/s^2)(3 s)=-29.4 m/s$

And since we know its mass, m=100 kg, we can find its momentum:

$p=mv=(100 kg)(-29.4 m/s)=-2940 kg m/s \cdot -3000 kg m/s$

and the negative sign simply means downward direction.

8 0

3 years ago

Which is true about using energy? There is an unlimited amount of energy in the universe. When energy is used, it disappears for

frutty [35]

Answer:

3. When energy is used, it can transform to new types but can never disappear.

Explanation: it can transform into heat, light, ect and will never disapear unlessed turned of.

7 0

3 years ago

A starship travels to a planet that is 20 light years away. The astronauts stay on the planet for 2.0 years before returning at

ad-work [718]

Answer:

astronauts age is 32 years

correct option is e 32 years

Explanation:

given data

travels = 20 light year

stay = 2 year

return = 52 years

to find out

astronauts aged

solution

we know here they stay 2 year so time taken in traveling is

time in traveling = ( 52 -2 ) = 50 year

so it mean 25 year in going and 25 years in return

and distance is given 20 light year

so speed will be

speed = distance / time

speed = 20 / 25 = 0.8 light year

so time is

time = $\frac{t}{\sqrt{1-v^2} }$

time = $\frac{25}{\sqrt{1-0.8^2} }$

time = 15 year

so age is 15 + 2 + 15

so astronauts age is 32 years

so correct option is e 32 years

4 0

3 years ago