A block of mass 4.0 kg rests on a horizontal surface where the coefficient of kinetic friction between the two is 0.20.A string attached to the block is pulled horizontally,resulting in a 3.0-m/s² acceleration by the block.Find the tension in the string.(g = 9.80 m/s²) A)12 N B)7.8 N C)20 N D)4.2 N

Question

Quizplus · Accepted Answer

We can use Newton's second law to solve this problem. The force of friction opposing the motion is given by:
f_friction = friction coefficient * normal force
where the normal force is equal to the weight of the block:
f_gravity = m * g
where g is the gravitational acceleration.

The tension in the string is equal in magnitude to the net force acting on the block:
T - f_friction = m * a
where a is the acceleration of the block.

Substituting the values:
f_friction = 0.2 * m * g = 7.84 N
f_gravity = m * g = 39.2 N
T - f_friction = m * a
T - 7.84 N = 4.0 kg * 3.0 m/s^2
T = 20 N

Therefore, the correct answer is choice C (20 N).

A Block of Mass 4