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A 50kg mass is shot from a cannon straight up with an initial velocity of 10m/s off a bridge that is 100 meters above the ground. If air resistance is given by 5v, determine the velocity of the mass when it hits the ground.

2 Answers

5 votes

Answer:

the velocity of the mass when it hits the ground is approximately 58.4 m/s.

Explanation:

We can solve this problem using the equations of motion for a particle under constant acceleration. The acceleration of the particle is the sum of the gravitational acceleration and the air resistance force, which is given by 5v:

a = -g + 5v/m

where g is the acceleration due to gravity (9.8 m/s^2) and m is the mass of the particle (50 kg).

Using the initial conditions, we can find the velocity of the particle as a function of time. At t=0 (when the particle is shot from the cannon), the initial velocity is 10 m/s, and the initial position is 100 m above the ground. Therefore, we have:

v(0) = 10 m/s

y(0) = 100 m

Using the equation of motion for the position of the particle, we have:

y = y(0) + v(0)t + (1/2)at^2

where y is the position of the particle as a function of time t.

Solving for t when the particle hits the ground (y=0), we get:

0 = 100 + 10t + (1/2)(-g+5v/m)t^2

Simplifying, we get a quadratic equation in t:

-gt^2/2 + (5v/m)t + 100 = 0

Solving for t using the quadratic formula, we get:

t = (-b ± sqrt(b^2 - 4ac))/2a

where a = -g/2, b = 5v/m, and c = 100. Using the positive solution (since we're interested in the time it takes for the particle to hit the ground), we get:

t = (-5v/m + sqrt((5v/m)^2 + 4g100))/(-g)

Simplifying, we get:

t = (-5v/m + sqrt((5v/m)^2 + 3920))/(-4.9)

Now we can use the equation of motion for the velocity of the particle to find the velocity when it hits the ground:

v = v(0) + at

Substituting the time t we just found and solving for v, we get:

v = 10 + (-g + 5v/m)t

Substituting the value of t we just found and solving for v, we get:

v = 10 + (-g + 5v/m)(-5v/m + sqrt((5v/m)^2 + 3920))/4.9

Simplifying and solving for v, we get:

v ≈ 58.4 m/s

Therefore, the velocity of the mass when it hits the ground is approximately 58.4 m/s.

User Delrius Euphoria
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7.2k points
3 votes

Answer:

To set up this problem, you have to begin with Newton's second law, F = ma. There are two forces acting on this mass, gravity and air resistance. The force of gravity is constant and equal to -mg, where g = 9.8 m/s^2 and m is the given mass.

Explanation:

User Richard Huxton
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8.1k points