A rope is used to pull a 3.57 kg block at constant speed 5.10 m along a horizontal floor. The force on the block from the rope is 6.82 N and is directed 15° above the horizontal.
(a)What is the work done by the rope's force?
(b) What is the increase in the thermal energy of the block-floor system?
(c) What is the coefficient of kinetic friction between the block and floor?
a) 6.82N * cos 15 * 5.1 m = ___ Joules
b) The same, since KE does not increase
c) 6.82 cos15/(M g) = 0.188
To find the answers to the given questions, we need to use the concepts of work, energy, and friction. Let's tackle each question step by step:
(a) What is the work done by the rope's force?
To calculate the work done by the rope's force, we'll use the formula:
Work = Force * Distance * cos(theta)
Here,
Force = 6.82 N (given)
Distance = 5.10 m (given)
theta = 15° (given angle above the horizontal)
Substituting the given values into the formula:
Work = 6.82 N * 5.10 m * cos(15°)
Now, calculate the value of cos(15°) using a calculator, which is approximately 0.9659.
Work ≈ 6.82 N * 5.10 m * 0.9659
Therefore, the work done by the rope's force is approximately:
Work ≈ 33.93 J
(b) What is the increase in the thermal energy of the block-floor system?
Since the block is moving at a constant speed, there is no net work done on the block. Therefore, the increase in thermal energy is zero.
The increase in thermal energy of the block-floor system is approximately:
ΔThermal Energy ≈ 0 J
(c) What is the coefficient of kinetic friction between the block and floor?
To find the coefficient of kinetic friction, we'll use the formula:
Force of friction = Normal force * coefficient of friction
Since the block is moving at a constant speed, the force of friction must be equal to the force applied by the rope, which is 6.82 N (given).
So, we can rewrite the equation as:
6.82 N = Normal force * coefficient of friction
The normal force is the force perpendicular to the floor, which is equal to the weight of the block, given by:
Normal force = mass * gravity
Here,
mass = 3.57 kg (given)
gravity is approximately 9.8 m/s².
Substituting the values into the equation:
6.82 N = (3.57 kg * 9.8 m/s²) * coefficient of friction
Simplifying the equation:
coefficient of friction = 6.82 N / (3.57 kg * 9.8 m/s²)
Therefore, the coefficient of kinetic friction between the block and the floor is approximately:
coefficient of friction ≈ 0.193
So, the coefficient of kinetic friction is approximately 0.193.
To find the answers to these questions, we'll use the following formulas:
(a) The work done by a force is given by the equation: Work = Force × Displacement × cos(theta), where theta is the angle between the force and displacement vectors.
(b) The increase in thermal energy of the block-floor system can be found using the equation: ∆E_thermal = Work - µ * m * g * d, where µ is the coefficient of kinetic friction, m is the mass of the block, g is the acceleration due to gravity, and d is the distance traveled by the block.
(c) The coefficient of kinetic friction can be determined using the equation: µ = (Force of friction) / (Normal force).
Now let's calculate the answers step by step:
(a) Work = Force × Displacement × cos(theta)
= 6.82 N × 5.10 m × cos(15°)
≈ 33.538 J
Therefore, the work done by the rope's force is approximately 33.538 J.
(b) ∆E_thermal = Work - µ * m * g * d
= 33.538 J - µ * 3.57 kg * 9.81 m/s² * 5.10 m
To find the increase in thermal energy, we need to calculate the coefficient of kinetic friction (µ) first.
(c) µ = (Force of friction) / (Normal force)
The normal force can be calculated as the weight of the block, which is given by m * g.
Normal force = 3.57 kg × 9.81 m/s²
Force of friction = µ * Normal force, but since the block is moving at a constant speed, the force of friction must be equal to the force applied by the rope.
6.82 N = µ * (3.57 kg × 9.81 m/s²)
Now we can solve for µ:
µ = 6.82 N / (3.57 kg × 9.81 m/s²)
≈ 0.1905
Therefore, the coefficient of kinetic friction between the block and the floor is approximately 0.1905.
Now we can go back to (b) and calculate the increase in thermal energy:
∆E_thermal ≈ 33.538 J - 0.1905 * 3.57 kg * 9.81 m/s² * 5.10 m
After substituting the values, you can calculate the final answer.