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Pani-rosa [81]
3 years ago
14

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?
Physics
1 answer:
Maslowich3 years ago
7 0

Answer:

16km/h

Explanation:

Vt=20km/h ---train speed

Vd=4km/h

Donas speed relative to ground is:

Vrd=Vt-Vd

Donas is moving in opposite direction of train .

Vrd=20km/h-4km/h

Vrd=16km/h

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A cyclist is coasting at 15 m/s when she starts down a 450 m long slope that is 30 m high. The cyclist and her bicycle have a co
Flura [38]

Answer:

Her speed at the bottom of the slope is 25.665 m/s

Explanation:

Here we have

Initial velocity, v₁= 15 m/s

Final velocity = v₂

The energy balance present in the system can be represented as

\frac{1}{2}mv_2^2 -\frac{1}{2}mv_1^2 - mgh = W

Where:

m = Mass of the cyclist = 70 kg

W = work done by the drag force = -F_Dd

Where:

d = Distance traveled = 450 m

Therefore,

\frac{1}{2}mv_2^2 -\frac{1}{2}mv_1^2 - mgh = -F_Dd and

v_2^2 =\frac{ \frac{1}{2}mv_1^2 + mgh  -F_Dd}{ \frac{1}{2}m}  = v_1^2 + 2gh -\frac{   2F_Dd}{ m} = 15^2 + 2\times 9.8\times 30 - \frac{2\times 12\times 450}{70}

= 658.714 m²/s²

v₂ = 25.665 m/s

Her speed at the bottom of the slope = 25.665 m/s.

6 0
3 years ago
The asteroid, Ida, has a small moon, Dactyl, that orbits at a speed of 5.66 m/s in an orbit of radius 90, 000m . What is Ida's m
cricket20 [7]

Answer:

4.3 x 10^16 kg

Explanation:

M = rv^2/G =[90,000 x 5.66^2] / [6.67 x 10^-11]

M = 43,226,446,776,611,694 = 4.3 x 10^16 kg - Ida's mass.

4 0
3 years ago
The combustion of propane (C3H8) in the presence of excess oxygen yields CO2 and H2O: C3H8 (g) + 5O2 (g) → 3CO2 (g) + 4H2O (g) W
zimovet [89]

Answer:

1.2

Explanation:

2.0 mol O₂ × (3 mol CO₂ / 5 mol O₂) = 1.2 mol CO₂

4 0
3 years ago
It has been suggested that a heat engine could be developed that made use of the fact that the temperature several hundred meter
lesantik [10]

Answer:

efficiency = 5.4%

Explanation:

Efficiency of heat engine is given as

\eta = \frac{W}{Q_{in}}

now we will have

W = Q_1 - Q_2

so we will have

\eta = 1 - \frac{Q_2}{Q_1}

now we know that

\frac{Q_2}{Q_1} = \frac{T_2}{T_1}

so we have

\eta = 1 - \frac{T_2}{T_1}

\eta = 1 - \frac{273+6}{273+22}

\eta = 0.054

so efficiency is 5.4%

8 0
3 years ago
What must you do to calculate a meaningful value of distance from the following equation?
ss7ja [257]

Answer:

Convert all the times to either hours or seconds

Explanation:

One time unit is in hours, and the other is in seconds.  In order to do the math, the units need to be the same.  So you either need to convert hours to seconds, or seconds to hours.

5 0
3 years ago
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