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pashok25 [27]
3 years ago
10

Dana is on a train traveling at a speed of 20 km/h. Dana walks from the front of the train to the back of the train at a speed o

f 4 km/h. What is Dana’s speed relative to the ground?
a.) 20 km/h
b.) 12 km/h
c.) 16 km/h
d.) 24 km/h
Physics
1 answer:
Angelina_Jolie [31]3 years ago
4 0

Answer:

Option C

16 Km/h

Explanation:

Dana is moving in opposite direction compared to the train.If we denote w-velocity of train with respect to ground and u- velocity of passenger with respect to train and v-velocity of passenger we can using classical mechanics claim that v = w-u

v=20-4=16 km/h

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Answer either one or both questions! Must explain and show work to receive brainliest!
MariettaO [177]
<span>F x L = W x X whereW=weight is total load = 80, L is length from fulcrum which is the unknown and what we are solving for. x= length we know. and F equals 50 force we know. So (W*X)/F=LL equals 64</span>
3 0
3 years ago
The haystack maker tractor lifted 120 kg of grass to a height of 5 meters in 6 seconds. Calculate the power of the haystack make
Gelneren [198K]

Answer:

1000 Joules per second.

Explanation:

To lift that much grass 5 meters higher than it was before the tractor did work that is the product of the (force needed to overdo gravity) and (displacement):

W = mg\Delta h=120kg\cdot 10\frac{m}{s^2}\cdot 5m = 6000J

Power is work over the amount of time:

P = \frac{W}{\Delta t}=\frac{6000J}{6 s} = 1000 \frac{J}{s}

4 0
3 years ago
Thallium consists of 29.5%TI-203 and 70.5%TI-205. What is the relative atomic mass of thallium?
Kazeer [188]
Since you are referring to the TI-203 and TI-205, you need to know the actual masses of these two isotopes. TI-203 has 202.9723 amu  and TI-205 has 204.9744 amu. Since you are concluding that this Thallium have 29.5% (Ti-203) and 70.5% (Ti-205), you need to multiply the percentage to the actual masses of the isotopes. With that, you should be able to get 204.3833 amu
7 0
2 years ago
Is it possible for the momentum of a system consisting of two carts on a low-friction track to be zero even if both carts are mo
choli [55]

Answer:

Yes, if the two carts are moving into opposite directions

Explanation:

The total momentum of the system of two carts is given by:

p=m_1 v_1 + m_2 v_2

where

m1, m2 are the masses of the two carts

v1, v2 are the velocities of the two carts

Let's remind that v (the velocity) is a vector, so its sign depends on the direction in which the cart is moving.

We want to know if it is possible that the total momentum of the system can be zero, so it must be:

p=0\\m_1 v_1 + m_2 v_2 = 0\\m_1 v_1 = -m_2 v_2

From this equation, we see that this condition can only occur if v1 and v2 have opposite signs. Opposite signs mean opposite directions: therefore, the total momentum can be zero if the two carts are moving into opposite directions.

4 0
3 years ago
Two billion people jump up in the air at the same time with an average velocity of 7.0 m/sec. If the mass of an average person i
faust18 [17]

Well first of all, you must realize that it depends on how the jumpers are distributed on the earth's surface.  If,say, one billion of them are in the eastern  hemisphere and the other billion are in the western one, then the sum of all of their momenta could easily be zero, and have no effect at all on the planet.  I'm pretty sure what you must have in mind is to consider the Earth to be a block, with a flat upper surface, and all the people jump in the same direction.

average mass per person = 60 kg.
jump velocity = 7 m/s straight up and away from the block, all in the same direction
one person's worth of momentum = (m) (v) = 420 kg.m/s
sum of two billion of them = 8.4 x 10¹¹ kg-m/s all in the same direction

Earth's "recoil" momentum = 8.4 x 10¹¹ in the opposite direction = (m) (v)

Divide each side by 'm' :     v = (momentum) / (mass) =

The Earth's "recoil" velocity is   (8.4 x 10¹¹) / (5.98 x 10²⁴) = 

                                                               1.405 x 10⁻¹³ m/s =

                                              <em> 0.00000000014 millimeter per second

</em>
I have no intuitive feeling for this kind of thing, so can't judge whether
the answer is reasonable.  But my math and physics felt OK on the
way to the solution, so that's my answer and I'm sticking to it.

4 0
3 years ago
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