Final answer:
The force pulling the block backward can be calculated using Newton's second law of motion. The force of friction, which can be determined by multiplying the coefficient of friction by the normal force, opposes the block's motion. By substituting the given values into the formulas, the force pulling the block backwards is approximately 1.2544 N.
Step-by-step explanation:
The force pulling the block backwards can be calculated using Newton's second law of motion, which states that the net force acting on an object is equal to its mass multiplied by its acceleration. In this case, the block has a mass of 0.64 kg and is accelerating to the right at a rate of 4.78 m/s². As the block is accelerating to the right, the force pulling it backwards is the force of friction.
To calculate the force of friction, we can use the formula:
Force of friction = μ * Normal force
where μ is the coefficient of friction and the normal force is equal to the weight of the block. The weight of the block can be calculated using the formula:
Weight = mass * acceleration due to gravity
Substituting the given values, we have: Weight = 0.64 kg * 9.8 m/s² = 6.272 N
Next, we can calculate the normal force:
Normal force = Weight = 6.272 N
Finally, substituting the values of coefficient of friction and normal force into the formula for force of friction, we have:
Force of friction = 0.20 * 6.272 N = 1.2544 N
Therefore, the force pulling the block backwards is approximately 1.2544 N.