Answer:
B.) a wheel and axle and a lever
Explanation:
P.S - The exact question is -
Given - A wheelbarrow can be used to help lift a load, such as a pile of dirt, and then push the load across a distance. A man pushes a wheelbarrow.
To find - Which simple machines make up a wheelbarrow?
A.) a pulley and an inclined plane
B.) a wheel and axle and a lever
C.) a pulley and a wheel and axle
D.) a lever and a wedge
Proof -
The correct option is - B.) a wheel and axle and a lever
Wheelbarrows are used to carry more goods from place to place by using minimal force as compared when goods are carried by hand.
With this machine, During hauling people can save time.
The momentum of block B afterwards is 
.
Explanation:
We can solve this problem by applying the principle of conservation of momentum.
In fact, the total momentum before and after the collision must be conserved. Therefore, we can write:
where:
is the initial momentum of block A
is the initial momentum of block B
is the final momentum of block A
is the final momentum of block B
Solving for , we find:
So, the momentum of block B afterwards is .
Learn more about momentum:
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<h2>
Answer: dark matter</h2>
It is believed that the Milky Way has 90% dark matter and only 10% ordinary matter (known matter). Because, like gravity, <u>dark matter can not be observed directly</u>, however its existence is inferred through the movement of the stars and the cosmic dust within the galaxy.
It is important to note that dark matter composition is unknown and corresponds to 80% of the matter in the universe. It does not emit or interact with any type of electromagnetic radiation, but it interacts with the known matter through gravity.
