P2.2 Forces

Question 1

What is a force?

Answer 1

A force is a push or a pull that can change the shape of an object or change its motion or its state of rest

Question 2

What is force measure in?

Answer 2

The unit of force is the newton (N)

Question 3

What happens when two objects interact? (Newton’s third law)

Answer 3

They will always exert equal and opposite forces on each other (for every action, there is an equal and opposite reaction)

Question 4

What is a resultant force?

Answer 4

A single force that has the same effect as all the forces acting on an object / the overall force

Question 5

What happens if the resultant force is:
1. Zero
2. Not zero
(Newton’s first law)

Answer 5

Zero: the object stays at rest or at constant velocity

Not zero: the velocity of the object will change

Question 6

What is the resultant force when the forces are acting in the same direction?

Answer 6

The sum of the forces

Question 7

What is the resultant force when forces are acting in different directions?

Answer 7

The difference between the forces

Question 8

The bigger the resultant force on an object is …

acceleration

Answer 8

… the greater its acceleration is

Question 9

The greater the mass of an object is …

acceleration

Answer 9

… the smaller its acceleration is (for a given force)

Question 10

What is the equation for force (resultant force)?

Answer 10

(resultant) Force(N) = mass(kg) x acceleration(m/s/s)

Question 11

In a car what are the opposing forces to the driving force?

Answer 11

friction and air resistance

Question 12

What is the stopping distance?

Answer 12

the minimum distance that a car can safely stop in

Question 13

What is breaking distance?

Answer 13

the distance travelled by the vehicle during the time the breaking force acts

Question 14

What is thinking distance?

Answer 14

the distance travelled by the vehicle in the time is takes the driver to react

Question 15

What is the equation for stopping distance?

Answer 15

stopping distance=thinking distance+breaking distance

Question 16

What are the factors that will affect breaking distance?

Answer 16

speed, weather, road conditions (all due to friction)

Question 17

What are the factors that will affect thinking distance?

Answer 17

alcohol, tiredness/fatigue, speed, distraction, medications, reaction time

Question 18

What is weight and its unit?

Answer 18

the weight of an object is the force of gravity on it - Newtons (N)

Question 19

What is mass and its unit?

Answer 19

the mass of an object is the quantity of mater in it - Kilograms (kg)

Question 20

What is the equation for weight?

Answer 20

Weight(N) = mass(kg) x gravitational field strength(N/kg)

Question 21

What is the terminal velocity of a falling object?

Answer 21

the velocity it reaches when it is falling in a fluid, the weight is then equal to the drag force

Question 22

What is extension?

Answer 22

length when stretched - its original length

Question 23

What is Hooke’s law (for elastic behavior)?

Answer 23

F=ke

Force(N)=spring constant(N/m) x extension(m)

Question 24

What is the spring constant (from Hooke’s law)?

Answer 24

the spring constant of a spring is the force per unit of extension needed to stretch it

Question 25

What can be said about the extension of an object and the force applied to it?

Answer 25

They are directly proportional, provided that the limit of proportionality is not exceeded

Question 26

How can fuel economy of road vehicles be improved?

Answer 26

reducing the speed

fitting a wind deflector

Question 27

What are anti-skid surfaces?

Answer 27

Anti-skid surfaces increase the friction between a car tyre and the road surface. This reduces skids, or even prevents skids altogether.