A stone on ground is zero energy
1 answer:
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Answer:
The coefficient of kinetic friction is 0.13
Explanation:
Newton's second law states that the acceleration of an object is proportional to the net force on it, the factor of proportionality is the mass. So, we can express that law mathematically as:
(1)
With F the net force, m the mass and a the acceleration of the object. In our case we're interested on what's happening to the sled, then we have to analyze the forces on it, those forces are the weight and the normal force on the vertical direction and the pulling force and frictional force in the horizontal direction. So, because (1) is a vector equation we can express that in their vertical (y) and horizontal (x) components:
(2)
(3)
On y we have that the acceleration is zero because the sled is not moving upward or downward, remember that the net force on y is the weight (W) pointing downward and the normal force pointing upward:
Following the convention that positive is upward and negative downward, W=mg=(755)(-9.81):
(4)
Now on the x direction we have the sum of the forces is the pulling force (T) and friction force (f)
Choosing the direction where the horse is pulling F=1988N and the acceleration should be positive too, then:
The negative sign means it's in the opposite direction the horse is pulling
The frictional force is related with the coefficient of kinetic friction in the next way:
with μk the coefficient of kinetic friction, and n the normal force that we already found on (4), so we simply solve the last equation for μk:
Answer:
(a) The maximum height achieved by the first ball, m₁ is 0.11 m
(a) The maximum height achieved by the second ball, m₂ ball is 0.44 m
Explanation:
Given;
mass of the first ball, m₁ = 1 kg
mass of the second ball, m₂ = 2 kg
The velocity of the first when released from a height of 1 m before collision;
u₁² = u₀² + 2gh
u₀ = 0, since it was released from rest
u₁² = 2gh
u₁² = 2 x 9.8 x 1
u₁² = 19.6
u₁ = √19.6
u₁ = 4.427 m/s
The velocity of the second ball before collision, u₂ = 0
Apply the principle of conservation of linear momentum, to determine the velocity of the balls after an elastic collision.
m₁u₁ + m₂u₂ = m₁v₁ + m₂v₂
where;
v₁ is the final velocity of the first ball after an elastic collision
v₂ is the final velocity of the second ball after an elastic collision
m₁u₁ + m₂(0) = m₁v₁ + m₂v₂
m₁u₁ = m₁v₁ + m₂v₂
1 x 4.427 = v₁ + 2v₂
v₁ + 2v₂ = 4.427
v₁ = 4.427 - 2v₂ ----- equation (1)
one directional velocity;
u₁ + v₁ = u₂ + v₂
u₂ = 0
u₁ + v₁ = v₂
v₁ = v₂ - u₁
v₁ = v₂ - 4.427 ------ equation (2)
Substitute v₁ into equation (1)
v₂ - 4.427 = 4.427 - 2v₂
3v₂ = 4.427 + 4.427
3v₂ = 8.854
v₂ = 8.854 / 3
v₂ = 2.95 m/s (→ forward direction)
v₁ = v₂ - 4.427
v₁ = 2.95 - 4.427
v₁ = - 1.477 m/s
v₁ = 1.477 m/s ( ← backward direction)
Apply the law of conservation of mechanical energy
(a) The maximum height achieved by the first ball (v₁ = 1.477 m/s)
(b) The maximum height achieved by the second ball (v₂ = 2.95 m/s)