Question

an object is placed on a frictionless horizontal surface. a constant horizontal force of 80 Newton is applied to the object. the block starts from rest and moves 11.0 miles in 5.00 seconds. (a) what is the mass of the object? (b) if the force is withdrawn at the end of 5 seconds, how far does the block move in the next 5 seconds?

Answer 1

(a) A constant force produces a constant acceleration, so the motion of the object is uniformly accelerated motion. The motion is governed by the kinematic equations for uniformly accelerated motion. The distance covered by the object in time t is given by

Given the object starts from rest we get

Solving for acceleration we get

Substituting and t = 5.00s we get

The mass, force, and acceleration are related by Newton's second law of motion F=ma, we have

(b) The final velocity of the object is

Given the object starts from rest we get

The velocity after 5 seconds is

When the force was removed the object was traveling at 7080 m/s. The distance covered by the object in the next 5 seconds is

Using 1 mile = 1609 m we get