P8 FORCES

Question 1

Newton’s First Law of Motion

Answer 1

An object will remain at rest or in uniform motion in a straight line unless acted upon by an external force.

Question 2

Newton’s Second Law of Motion

Answer 2

The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. (F = ma)

Question 3

Newton’s Third Law of Motion

Answer 3

For every action, there is an equal and opposite reaction.

Question 4

Resultant Force

Answer 4

The single force that represents the vector sum of all the forces acting on an object.

Question 5

Inertia

Answer 5

The tendency of an object to resist changes in its state of motion.

Question 6

Terminal Velocity

Answer 6

The constant speed that a freely falling object eventually reaches when the resistance of the medium prevents further acceleration.

Question 7

Weight

Answer 7

The force exerted on an object due to gravity. (Weight = mass × gravitational field strength, W = mg)

Question 8

Mass

Answer 8

A measure of the amount of matter in an object.

Question 9

Momentum

Answer 9

The product of an object’s mass and velocity. (p = mv)

Question 10

Conservation of Momentum

Answer 10

The total momentum of a closed system remains constant provided no external forces act on it.

Question 11

Free Body Diagram

Answer 11

A diagram showing all the forces acting on a single object.

Question 12

Explain how Newton’s First Law applies to passengers in a car that suddenly stops.

Answer 12

According to Newton’s First Law, passengers will continue moving forward at the car’s original speed due to inertia until an external force (like a seatbelt) acts on them.

Question 13

A skydiver reaches terminal velocity after falling for a period of time. Describe the forces acting on the skydiver at terminal velocity and why the speed remains constant.

Answer 13

At terminal velocity, the downward force of gravity is balanced by the upward force of air resistance, resulting in no net force and therefore constant speed.

Question 14

During a collision between two ice skaters, one skater pushes against the other. Using Newton’s Third Law, explain the forces experienced by both skaters.

Answer 14

According to Newton’s Third Law, when one skater exerts a force on the other, the second skater exerts an equal and opposite force on the first skater. Both skaters experience forces of equal magnitude but in opposite directions.

Question 15

How does the concept of inertia explain why passengers lurch forward when a car suddenly stops?

Answer 15

Inertia causes passengers to continue moving at the car’s previous speed even when the car stops, causing them to lurch forward.

Question 16

If a spacecraft is traveling in space far from any gravitational influence and its engines are turned off, describe its motion.

Answer 16

The spacecraft will continue moving at a constant velocity in a straight line because no external forces are acting on it to change its motion.