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Pepsi [2]
2 years ago
13

A bullet with a mass of 4.26 g and a speed of 881 m/s penetrates a tree horizontally to a depth of 4.44 cm. Assume that a consta

nt frictional force stops the bullet. Calculate the magnitude of this frictional force. Try energy considerations.
Physics
1 answer:
sveta [45]2 years ago
8 0

Let F be the magnitude of the frictional force. This force performs an amount of work W on the bullet such that

W = -Fx

where x is the distance over which F is acting. This is the only force acting on the bullet as it penetrates the tree. The work-energy theorem says the total work performed on a body is equal to the change in that body's kinetic energy, so we have

W = ∆K

-Fx = 0 - 1/2 mv²

where m is the body's mass and v is its speed.

Solve for F and plug in the given information:

F = mv²/(2x)

F = (0.00426 kg) (881 m/s)² / (2 (0.0444 m))

F = 37,234.8 N ≈ 37.2 kN

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A motion sensor emits sound, and detects an echo 0.0115 s after. A short time later, it again emits a sound, and hears an echo a
Mekhanik [1.2K]

Answer:

1.17 m

Explanation:

From the question,

s₁ = vt₁/2................ Equation 1

Where s₁ = distance of the reflecting object for the first echo, v = speed of the sound in air, t₁ = time to dectect the first echo.

Given: v = 343 m/s, t = 0.0115 s

Substitute into equation 1

s₁ = (343×0.0115)/2

s₁ = 1.97 m.

Similarly,

s₂ = vt₂/2.................. Equation 2

Where s₂ = distance of the reflecting object for the second echo, t₂ = Time taken to detect the second echo

Given: v = 343 m/s, t₂ = 0.0183 s

Substitute into equation 2

s₂ = (343×0.0183)/2

s₂ = 3.14 m

The distance moved by the reflecting object from s₁ to s₂ = s₂-s₁

s₂-s₁ =  (3.14-1.97) m = 1.17 m

7 0
3 years ago
Read 2 more answers
An elevator is moving is an upwards
Minchanka [31]

Answer:

The elevator's free-body diagram has three forces, the force of gravity, a downward normal force from you, and an upward force from the tension in the cable holding the elevator. The combined system of you + elevator has two forces, a combined force of gravity and the tension in the cable.

Explanation:

6 0
3 years ago
During a neighborhood baseball game in a vacant lot, a particularly wild hit sends a 0.148 kg baseball crashing through the pane
mr_godi [17]

Explanation:

Mass of baseball, m = 0.148 kg

Initial speed of the ball, u = 14.5 m/s

Final speed of the ball, v = 11.5 m/s

After crashing through the pane of a second-floor window, the ball shatters the glass as it passes through, and leaves the window at 11.5 m/s with no change of direction. So, the direction of the impulse that the glass imparts to the baseball is in opposite direction to the direction of the balls path.

The change in momentum of the ball is called impulse. It is given by :

J=m(v-u)\\\\J=0.148\times (11.5-14.5) \\\\J=-0.444\ kg-m/s\\\\|J|=0.444\ kg-m/s

Hence, this is the required solution.

3 0
3 years ago
The half-life of the radioactive isotope Carbon-14 is about 5730 years. Find N in terms of t. The amount of a radioactive elemen
Fudgin [204]

The complete queston is The amount of a radioactive element A at time t is given by the formula

A(t) = A₀e^kt

Answer:  A(t) =N e^( -1.2 X 10^-4t)

Explanation:

Given

Half life =  5730 years.

A(t) =A₀e ^kt

such that

A₀/ 2 =A₀e ^kt

Dividing both sides by A₀

1/2 = e ^kt

1/2 = e ^k(5730)

1/2 = e^5730K

In 1/2 =  5730K

k = 1n1/2 / 5730

k = 1n0.5 / 5730

K= -0.00012 = 1.2 X 10^-4

So that expressing   N in terms of t, we have

A(t) =A₀e ^kt

A₀ = N

A(t) =N e^ -1.2 X 10^-4t

7 0
3 years ago
Please help me i have this due tommorrow!!!
Ronch [10]
I found this!! maybe this will help :)

8 0
2 years ago
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