3 Forces and Motion

Question 1

Vector

Answer 1

A quantity that has a magnitude and a direction

Question 2

Scalar

Answer 2

A quantity that has a magnitude only

Question 3

Displacement

Answer 3

The distance travelled in a particular direction

Question 4

Velocity

Answer 4

The distance travelled in a certain direction per unit time

Question 5

Speed

Answer 5

The distance travelled per unit time

Question 6

Average Speed

Answer 6

The overall distance travelled divided by the time taken

Question 7

Acceleration

Answer 7

The change in velocity per unit time

Question 8

Instantaneous Speed

Answer 8

The speed at any particular instant in time

Question 9

1 Newton

Answer 9

The force required to give a mass of 1kg an acceleration of 1ms^2 in the direction of the force

Question 10

Drag force / Frictional Force

Answer 10

The force on an object which opposes the motion of the object, or the tendency of the object to move

Question 11

Weight

Answer 11

The gravitational force acting on an object

Question 12

Terminal Velocity

Answer 12

The constant velocity of an object, achieved when the frictional forces balance the driving force

Question 13

Moment of a Force

Answer 13

A rotational force, given by the product of the force and the perpendicular distance from the pivot point

Question 14

A Couple

Answer 14

A pair of equal but opposite forces with lines of action separated by a distance. The couple tends to produce rotation only

Question 15

Torque of a Couple

Answer 15

The product of one of the forces in a couple and the perpendicular distance between them

Question 16

Equilibrium

Answer 16

The state of an object such that the total force and total moment acting on it are zero

Question 17

Stress

Answer 17

The applied force per unit area

Question 18

Strain

Answer 18

The extension produced per unit length

Question 19

Young’s Modulus

Answer 19

The stress per unit strain when a material is behaving elastically

Question 20

Ultimate Tensile Strength

Answer 20

The maximum possible stress applied to a material before fracture

Question 21

Elastic Deformation

Answer 21

Deformation which is fully recovered when the force on an object is removed

Question 22

Plastic Deformation

Answer 22

Deformation which is NOT fully recovered when the force on an object is removed

Question 23

Centre of Mass

Answer 23

The point where the entire weight of an object appears to act

Question 24

Thinking Distance

Answer 24

The distance a vehicle will travel during the time the driver reacts to a problem

Question 25

Thinking Time

Answer 25

The time taken for the driver to react to a problem and apply brake

Question 26

Braking Distance

Answer 26

The distance travelled by a vehicle from the moment the brakes are applied until the vehicle comes to a complete stop

Question 27

Braking Time

Answer 27

The time taken for a vehicle to come to a complete stop after the brakes have been applied

Question 28

Stopping Distance

Answer 28

The total distance taken for a vehicle to come to rest from the point where the incident is first seen. Given by the thinking distance plus the braking distance

Question 29

Work Done

Answer 29

The amount of energy converted from one form to another. The product of the applied force on an object and the distance over which the force is applied

Question 30

1 Joule

Answer 30

The kinetic energy of 2kg mass has when it moves a speed of 1m/s. The gravitational potential energy of 0.1kg mass has when held 1m above the Earth's surface

Question 31

Conservation of Energy

Answer 31

For an isolated system, the total energy is a constant value. Energy cannot be created or destroyed, only convert from one form to another

Question 32

Newton's 1st Law

Answer 32

An object will remain at rest or continue to travel at constant velocity unless acted on by an external force

Question 33

Newton's 2nd Law

Answer 33

The resultant force on an object is directly proportional to and in the same direction as its rate of change of linear momentum

Question 34

Newton's 3rd Law

Answer 34

For every force there is an equal but opposite force

Question 35

Linear Momentum

Answer 35

The product of the mass and velocity of an object

Question 36

Net Force on a Body

Answer 36

The rate of change of momentum

Question 37

Impulse

Answer 37

The change of momentum of an object. The product of the force on an object and the time over which the force acts

Question 38

Conservation of Linear Momentum

Answer 38

For an isolated system, the total linear momentum in any direction is a constant

Question 39

Perfectly Elastic Collisions

Answer 39

A collision with no change of Kinetic Energy

Question 40

Inelastic Collisions

Answer 40

A collision where Kinetic Energy changes

Question 41

Completely Inelastic Collisions

Answer 41

A collision where all of the kinetic energy is converted to other forms

Question 42

1 Watt

Answer 42

A transfer of energy at a rate of 1 joule per second

Question 43

Explain Galileo's experiment that overturned Aristotle's ideas of motion

Answer 43

He dropped objects of different mass but same size. He noted that the acceleration was the same in both cases and they have landed at the same time.

Question 44

Describe and explain how seat belts in cars reduce impact force on the driver in an accident

Answer 44

Prevents the driver hitting the steering wheel. Increases the time of the impact therefore reducing the force of the impact.

Question 45

State two conditions necessary for an object to be in equilibrium

Answer 45

Clockwise moment around a point = counterclockwise moment around the same point. Net moment and force = 0

Question 46

Newton's law of gravitaion

Answer 46

Force is proportional to the product of the masses and inversely proportional to the square of their seperation

Question 47

Hooke's law

Answer 47

Strain in a solid is proportional to the applied stress within the elastic limit of that solid.