Physics: Forces in Balance and Imbalance Worksheet

Question 1

A book rests on a table. Gravity pulls the book downward with a force of 12 N, and the table pushes upward with a force of 12 N. Are the forces balanced or unbalanced? Explain what happens to the book.

Accepted Answer

The forces are balanced because the upward force and downward force are equal. The net force is 0 N, so the book stays at rest on the table.

Question 2

Two students push a box in opposite directions. One student pushes right with 30 N, and the other pushes left with 20 N. What is the net force on the box, and which way will it accelerate?

Accepted Answer

The net force is 10 N to the right because 30 N minus 20 N equals 10 N. The box will accelerate to the right.

Question 3

A soccer ball is sitting still on the grass. A player kicks it, applying an unbalanced force. Describe how the motion of the ball changes.

Accepted Answer

The ball changes from being at rest to moving because the kick applies an unbalanced force. The ball accelerates in the direction of the kick.

Question 4

A rope in a tug-of-war has a team pulling left with 150 N and another team pulling right with 150 N. What is the net force on the rope? What does this mean for the rope's motion?

Accepted Answer

The net force on the rope is 0 N because the forces are equal and opposite. If the rope is not already moving, it will stay still.

Question 5

A toy car rolls across the floor. Friction pushes backward on the car. If no one keeps pushing the car forward, what will happen to its speed? Explain using forces.

Accepted Answer

The car will slow down because friction is an unbalanced force acting opposite the car's motion. This backward force causes the car to decelerate.

Question 6

A 40 N force pushes a desk to the right, and a 15 N friction force acts to the left. Calculate the net force on the desk.

Accepted Answer

The net force is 25 N to the right because 40 N minus 15 N equals 25 N.

Question 7

An elevator moves upward at a constant speed. The upward cable force equals the downward force of gravity. Are the forces balanced or unbalanced? Explain.

Accepted Answer

The forces are balanced because the upward and downward forces are equal. Since the elevator moves at a constant speed, its motion is not changing.

Question 8

A student says, "If an object is moving, there must be an unbalanced force on it." Is this statement always correct? Explain.

Accepted Answer

The statement is not always correct. An object can keep moving at a constant speed in a straight line when the forces on it are balanced.

Question 9

A cart has three forces acting on it: 25 N to the right, 10 N to the right, and 20 N to the left. What is the net force?

Accepted Answer

The total force to the right is 35 N. The net force is 15 N to the right because 35 N minus 20 N equals 15 N.

Question 10

A lamp hangs from the ceiling by a chain. Gravity pulls down on the lamp, and the chain pulls up with an equal force. What is the net force on the lamp, and why does it not fall?

Accepted Answer

The net force on the lamp is 0 N because the upward pull from the chain equals the downward pull of gravity. The lamp does not fall because the forces are balanced.

Question 11

A skateboarder pushes off the ground and begins moving forward. Identify the force that caused the change in motion and explain whether it was balanced or unbalanced.

Accepted Answer

The ground pushes the skateboarder forward after the skateboarder pushes backward on the ground. This forward force is unbalanced, so it changes the skateboarder's motion.

Question 12

A box is sliding to the right, but its speed is decreasing. What can you conclude about the direction of the net force on the box?

Accepted Answer

The net force must be to the left because the box is slowing down while moving right. A force opposite the motion causes deceleration.

Question 13

A balloon is released and shoots across the room as air rushes out. Explain why the balloon moves using the idea of unbalanced forces.

Accepted Answer

The air rushing out of the balloon pushes one way, and the balloon is pushed the opposite way. This creates an unbalanced force that accelerates the balloon across the room.

Question 14

Look at a force diagram where an object has 50 N upward and 50 N downward, plus 20 N left and 20 N right. What is the net force, and are the forces balanced?

Accepted Answer

The net force is 0 N because the vertical forces cancel and the horizontal forces cancel. The forces are balanced.

Question 15

A hockey puck glides on very smooth ice. It keeps moving nearly at a constant speed until it hits the boards. Explain why the puck keeps moving for a while even after the stick stops touching it.

Accepted Answer

The puck keeps moving because objects in motion stay in motion unless an unbalanced force changes their motion. On smooth ice, friction is small, so the puck does not slow down quickly.

Physics: Forces in Balance and Imbalance

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