Balanced and unbalanced forces Knowledge-Based Practice

Questions

1. 1.

   An airplane travels horizontally in a straight line at a constant velocity while its engines exert a forward thrust of 60,000 N. What is the magnitude of the total opposing drag force acting on the airplane?

   • A) 0 N
   • B) 60,000 N
   • C) 30,000 N
   • D) 120,000 N
2. 2.

   A crate is pulled across a flat, rough floor by a horizontal rope and speeds up as it moves to the right. Which statement correctly describes the horizontal forces acting on the crate?

   • A) The forward pulling force is equal in magnitude to the friction force, resulting in balanced horizontal forces.
   • B) The friction force is greater in magnitude than the forward pulling force, resulting in an unbalanced net force.
   • C) The forward pulling force is greater in magnitude than the friction force, resulting in an unbalanced net force.
   • D) The friction force drops to zero once the crate is moving, resulting in balanced horizontal forces.
3. 3.

   A book rests motionless on a flat, horizontal table. Which statement correctly explains why the vertical forces acting on the book are balanced?

   • A) The upward normal force exerted by the table is equal in magnitude and opposite in direction to the downward gravitational force on the book, producing a net force of zero.
   • B) The downward gravitational force and the upward normal force form an action-reaction pair that automatically cancels itself out on the book.
   • C) The upward normal force exerted by the table is greater than the book's weight to prevent the book from sinking into the surface.
   • D) Static friction between the book and the table counteracts the downward gravitational pull to keep the book stationary.
4. 4.

   A cart travels along a frictionless horizontal track to the right at a constant speed of 2 m/s. If a 5 N force to the right and a 5 N force to the left act on the cart simultaneously, how will its motion be affected?

   • A) The cart will immediately come to rest.
   • B) The cart will gradually slow down until it stops.
   • C) The cart will continue moving to the right at 2 m/s.
   • D) The cart will accelerate to the right because it already has forward momentum.
5. 5.

   An object experiences two horizontal forces: 5 N directed to the east and 8 N directed to the west. What single additional horizontal force must be applied to the object to make the forces balanced?

   • A) 3 N directed to the west
   • B) 13 N directed to the east
   • C) 3 N directed to the east
   • D) 13 N directed to the west
6. 6.

   An elevator is moving upward while slowing down to a stop. Which statement correctly describes the vertical forces acting on the elevator during this deceleration?

   • A) The forces are unbalanced, and the downward force of gravity is greater than the upward tension force.
   • B) The forces are balanced, because the elevator continues moving upward throughout the deceleration.
   • C) The forces are unbalanced, and the upward tension force is greater than the downward force of gravity.
   • D) The forces are balanced, because the elevator is gradually coming to rest.
7. 7.

   An object travels along a curved path at a constant speed. What must be true regarding the forces acting on the object?

   • A) The forces are balanced because the object's speed does not change.
   • B) No forces act on the object because its kinetic energy remains constant.
   • C) The forces are unbalanced because the object's direction of motion is changing.
   • D) The net force is zero because the forces cancel each other out during uniform motion.
8. 8.

   A stationary block on a frictionless surface experiences two horizontal forces: 18 N acting to the right and 12 N acting to the left. What is the net force acting on the block, and how does it affect the block's motion?

   • A) The net force is 30 N to the right, and the block remains at rest.
   • B) The net force is 0 N, and the block moves to the right at a constant velocity.
   • C) The net force is 6 N to the left, and the block accelerates to the left.
   • D) The net force is 6 N to the right, and the block accelerates to the right.
9. 9.

   Which of the following conditions must be met for the forces acting on an object to be classified as balanced?

   • A) All applied forces must act in the same direction so they combine constructively.
   • B) The forces must overcome friction and cause the object to decelerate to rest.
   • C) The forces must produce a non-zero net force in the direction of the object's motion.
   • D) The vector sum of all forces acting on the object must equal zero, producing no acceleration.
10. 10.

    Which of the following scenarios describes an object acted upon by an unbalanced force?

    • A) A picture frame hanging motionless on a wall
    • B) An airplane cruising at a constant speed, altitude, and direction
    • C) A book resting flat on a stationary desk
    • D) A bicycle slowing down as the rider applies the brakes
11. 11.

    A box slides across a smooth horizontal floor at a constant velocity in a straight line. Which statement correctly describes the forces acting on the box?

    • A) An unbalanced forward force is required to maintain the motion of the box.
    • B) The forces acting on the box are balanced because its velocity is not changing.
    • C) The net force on the box is directed forward because motion always indicates an unbalanced force.
    • D) Gravity is the only force acting on the box because horizontal forces disappear at constant speed.

Answers and step-by-step solutions appear after you finish the test.