A projectile fired upward from the Earth's surface will usually slow down, come momentarily to rest, and return to Earth. For a certain initial speed, however it will move upward forever, with its speed gradually decreasing to zero just as its distance from Earth approaches infinity. The initial speed for this case is called escape velocity. You can find the escape velocity v for the Earth or any other planet from which a projectile might be launched using conservation of energy. The projectile of mass m leaves the surface of the body of mass M and radius R with a kinetic energy Ki = mv²/2 and potential energy Ui = -GMm/R. When the projectile reaches infinity, it has zero potential energy and zero kinetic energy since we are seeking the minimum speed for escape. Thus Uf = 0 and Kf = 0. And from conservation of energy,
Ki + Ui = Kf + Uf
mv²/2 -GMm/R = 0
∴ v = √(2GM/R)
This is the expression for escape velocity.
(0.5)×(0squared)×(3)=(1.5j)
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Below are the choices the can be found elsewhere:
A.) 14 newtons upward
<span>B.) 45 newtons upward </span>
<span>C.) 67 newtons upward </span>
<span>D.) 130 newtons upward </span>
<span>E.) 150 newtons upward
</span>
The answer is A.) 14 newtons upward
Answer:
7kgm/s
Explanation:
Using the law of conservation of momentum which states that the sum of momentum of bodies before collision is equal to the sum of the bodies after collision.
Let P1A and P1B be the initial momentum of the bodies A and B respectively
Let P2A and P2B be the final momentum of the bodies A and B respectively after collision.
Based on the law:
P1A+P2A = P1B + P2B
Given P1A = 5kgm/s
P2A = 0kgm/s(ball B at rest before collision)
P2A = -2.0kgm/s (negative because it moves in the negative x direction)
P2B = ?
Substituting the values in the equation gives;
5+0 = -2+P2B
5+2 = P2B
P2B = 7kgm/s
Let's call
the mass of the glider and
the total mass of the seven washers hanging from the string.
The net force on the system is given by the weight of the hanging washers:
For Newton's second law, this net force is equal to the product between the total mass of the system (which is
) and the acceleration a:
So, if we equalize the two equations, we get
and from this we can find the acceleration:
