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dem82 [27]
4 years ago
8

a train travels 99 kilometers in 3 hours, and then 80 kilometers in 5 hours. What is it’s average speed?

Physics
1 answer:
Karolina [17]4 years ago
6 0

Average speed = (total distance covered) / (time to cover the distance)

Total distance covered = (99km + 80km) = 179 km

Time to cover the distance = 8 hours

Average speed = (179km / 8hours)

Average speed = 22.375 km/hour

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Two massless bags contain identical bricks, each brick having a mass M. Initially, each bag contains four bricks, and the bags m
stepladder [879]

Answer: F_{2}=\frac{3}{4}F_{1}

Explanation:

According to Newton's law of universal gravitation:

F=G\frac{m_{1}m_{2}}{r^2}

Where:

F is the module of the force exerted between both bodies

G is the universal gravitation constant.

m_{1} and m_{2} are the masses of both bodies.

r is the distance between both bodies

In this case we have two situations:

1) Two bags with masses 4M and 4M mutually exerting a gravitational attraction F_{1} on each other:

F_{1}=G\frac{(4M)(4M)}{r^2}   (1)

F_{1}=G\frac{16M^2}{r^2}   (2)

F_{1}=16\frac{GM^2}{r^2}   (3)

2) Two bags with masses 2M and 6M mutually exerting a gravitational attraction F_{2} on each other (assuming the distance between both bags is the same as situation 1):

F_{2}=G\frac{(2M)(6M)}{r^2}   (4)

F_{2}=G\frac{12M^2}{r^2}   (5)

F_{2}=12\frac{GM^2}{r^2}   (6)

Now, if we isolate \frac{GM^2}{r^2} from (3):

\frac{F_{1}}{16}=\frac{GM^2}{r^2}   (7)

Substituting \frac{GM^2}{r^2}  found in (7) in (6):

F_{2}=12(\frac{F_{1}}{16})   (8)

F_{2}=\frac{12}{16}F_{1}   (9)

Simplifying, we finally get the expression for F_{2}  in terms of F_{1} :

F_{2}=\frac{3}{4}F_{1}  

5 0
3 years ago
A roller coaster car of mass m = 300 kg is released from rest at the top of a 60 m high hill (position A), and rolls with a negl
Triss [41]

Answer:

The principle of conservation of energy and angular momentum

Explanation:

At point A, the car experienced maximum of potential energy

As it moves down the hill, the potential energy decreases while the kinetic energy increases.

The maximum kinetic energy of the car is needed for the attainment of enough centripetal force to help the car move through the loop without falling .

7 0
3 years ago
The landing of a spacecraft is cushioned with the help of airbags. During its landing on Mars, the velocity of downward fall is
statuscvo [17]
You can use the impulse momentum theorem and just subtract the two momenta.
P1 - P2 = (16-1.2)(11.5e4)=1702000Ns
If you first worked out the force and integrated it over time the result is the same
5 0
3 years ago
Read 2 more answers
State whether the following statement are true or false .
Klio2033 [76]
1. It’s true
4 ,7 ,8 is correct
5 0
3 years ago
Ian walks 2 km to his best friends house, then walks 0.5 km to the library. He then makes 2.5 km walk home. The entire walk took
allochka39001 [22]
1. 2+0.5+2.5= 3. 2km/hr average




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