Forces And motion

Question 1

What does it mean when an object is not moving?

Answer 1

It means the forces acting on it are balanced, not that no forces are acting on it.

Question 2

What are the two forces acting on a rock sitting on the ground?

Answer 2

The force of gravity (pulling it down) and the contact force from the ground (pushing up).

Question 3

Why doesn’t the rock move towards the center of the Earth?

Answer 3

Because the contact force from the ground balances the force of gravity.

Question 4

What happens when the wind pushes against the rock?

Answer 4

The wind’s pushing force is balanced by friction between the rock and the ground, preventing movement.

Question 5

How are forces represented in a force diagram?

Answer 5

With arrows that show the size and direction of each force; longer arrows represent stronger forces.

Question 6

What do equal-length arrows pointing in opposite directions represent in a force diagram?

Answer 6

Balanced forces.

Question 7

What happens when a rock is pushed with a force larger than friction?

Answer 7

The forces become unbalanced, and the rock will start to move.

Question 8

In the context of a force diagram, what indicates that forces are unbalanced?

Answer 8

When one arrow is longer than the other, indicating a stronger force in one direction.

Question 9

What happens to the rock when a large force, such as a vehicle, pushes it compared to just the wind?

Answer 9

When a large force pushes the rock, it overcomes the friction, resulting in unbalanced forces that cause the rock to move. When only wind pushes the rock, the force is balanced by friction, so the rock does not move.

Question 10

How do unbalanced forces affect the movement of the rock?

Answer 10

Unbalanced forces cause the rock to move in the direction of the larger force, as the friction is no longer sufficient to balance it.

Question 11

What effect do unbalanced forces have on a moving object?

Answer 11

Unbalanced or unequal forces can make a moving object slow down.

Question 12

How does a parachute affect a falling object?

Answer 12

The parachute creates a force of air resistance that is larger than the weight of the object, slowing it down.

Question 13

What happens to the forces acting on an object when a parachute first opens?

Answer 13

When the parachute first opens, air resistance is greater than the weight of the object, resulting in unbalanced forces that slow it down.

Question 14

What occurs once the falling object slows down due to the parachute?

Answer 14

The air resistance decreases until it matches the weight of the object, and the forces become balanced.

Question 15

What happens to the speed of the object when the forces acting on it become balanced again?

Answer 15

The object falls at a constant speed once the forces are balanced.

Question 16

How can balanced and unbalanced forces be represented in a force diagram of a parachute?

Answer 16

When the forces are unbalanced, the arrow for air resistance is longer than the arrow for weight. When balanced, the arrows for air resistance and weight are equal.

Question 17

What can unbalanced forces cause an object to do?

Answer 17

Unbalanced forces can make an object change direction.

Question 18

How does a tennis ball change direction when hit by a racket?

Answer 18

When the ball contacts the racket, the hitting force must be larger than the force from the ball to make it change direction, resulting in an unbalanced force.

Question 19

In a force diagram of a tennis ball hitting a racket, what do the arrows represent?

Answer 19

The arrows represent the hitting force on the ball and the force from the ball on the racket, indicating the interaction and change in direction.

Question 20

How does the force of gravity affect the movement of planets around the Sun?

Answer 20

The force of gravity is a constant, unbalanced force that keeps planets in orbit around the Sun.

Question 21

Why is a constant unbalanced force needed for an object to move in a circle?

Answer 21

When an object moves in a circle, its direction is always changing, so a constant unbalanced force is required to maintain circular motion.

Question 22

In the diagram of a planet orbiting the Sun, what does the arrow pointing towards the Sun represent?

Answer 22

The arrow represents the force of gravity from the Sun, which constantly changes the direction of the planet’s movement, keeping it in orbit.

Question 23

When are forces considered balanced?

Answer 23

Forces are balanced when they are equal in size and opposite in direction.

Question 24

What happens to an object’s movement when balanced forces act on it?

Answer 24

There is no change in the object’s movement.

Question 25

What makes forces unbalanced?

Answer 25

Forces are unbalanced when they are not equal in size and/or act in directions that are not opposite.

Question 26

What are the effects of unbalanced forces on an object’s movement?

Answer 26

Unbalanced forces cause a change in movement, such as speeding up, slowing down, or changing direction.

Question 27

What type of movement change occurs when forces are equal but not opposite?

Answer 27

The forces are unbalanced, causing a change in direction.

Question 28

What change in movement occurs when forces are not equal and opposite?

Answer 28

The unbalanced forces result in an increase in speed or slowing down.

Question 29

What is meant by “balanced forces”?

Answer 29

Balanced forces are forces that are equal in size and opposite in direction, causing no change in the movement of the object.

Question 30

Describe a force diagram for a box on the floor that is not moving.

Answer 30

A force diagram for the box should show the downward force of gravity and the upward contact force from the floor, which are balanced.

Question 31

What happens if Amal pushes a box sideways and it does not move?

Answer 31

The forces acting on the box are still balanced, which includes the push from Amal being balanced by the friction force between the box and the floor.

Question 32

In a tug of war, what must happen for one team to win?

Answer 32

The team must exert a greater (unbalanced) force to pull the rope in their direction, overcoming the opposing force from the other team.

Question 33

Why is the rope not moving when both Team A and Team B are pulling on it in a tug of war?

Answer 33

The rope is not moving because the forces exerted by both teams are equal in size but opposite in direction, resulting in balanced forces.

Question 34

What two changes could make the rope move towards Team B in a tug of war?

Answer 34

Team B could either increase their pulling force or Team A could decrease their pulling force, resulting in unbalanced forces that make the rope move towards Team B.

Question 35

Why is the aeroplane in the diagram flying at a constant speed and not getting higher or lower?

Answer 35

The forces acting on the aeroplane—thrust, drag, lift, and weight—are balanced. Thrust equals drag, maintaining constant speed, and lift equals weight, keeping it at the same altitude.

Question 36

Which force should increase to make the aeroplane go faster?

Answer 36

The thrust should increase to make the aeroplane go faster.

Question 37

Which force should increase to make the aeroplane go higher or gain lift?

Answer 37

The lift should increase to make the aeroplane go higher.

Question 38

Which force should decrease to make the aeroplane go lower?

Answer 38

The lift should decrease to make the aeroplane go lower.

Question 39

Which force should decrease to make the aeroplane go faster?

Answer 39

The drag should decrease to make the aeroplane go faster.

Question 40

In the toy train moving around a circular track, what is the direction of the driving force of the train?

Answer 40

The driving force of the train is shown by the arrow labeled A.

Question 41

Which arrow shows the force of friction on the locomotive of the toy train?

Answer 41

The force of friction is shown by the arrow labeled B.

Question 42

Which arrow shows the force that keeps the toy train moving in a circle?

Answer 42

The force that keeps the toy train moving in a circle is shown by the arrow labeled C.