Forces and Motion

Question 1

What is the Centre of Gravity

Answer 1

An imaginary point where the entire weight of an object appears to act

Question 2

What is the Centre of Mass

Answer 2

A point through which any externally applied forces produces a straight line motion but no rotation

Question 3

What Idea is the Centre of Gravity Practical Based on?

Answer 3

A freely suspended object will come to rest with its centre of gravity vertically below the point of suspension

Question 4

What is the moment of the force dependent on?

Answer 4

• The magnitude of the force acting• The perpendicular distance from the pivot that the forces act

Question 5

Moments Equation

Answer 5

Moment = Force x Perpendicular Distance M = Fd

Question 6

What does it mean if an object is in equilibrium? (Principle of Moments)

Answer 6

The sum of the clockwise moments about a pivot must equal the sum of the anti-clockwise momentsIt makes no difference at which point the moments are taken

Question 7

What is a couple?

Answer 7

Two forces that are equal and opposite to each other but are not on the same straight line

Question 8

Torque Equation

Answer 8

Torque = One of the forces x perpendicular distance between both forces 2 x F x 1/2d = ↩️A = Torque

Question 9

What is Kinetic Energy?

Answer 9

Where movement is taken place

Question 10

What is Potential Energy?

Answer 10

Regions where electric, magnetic, gravitation, and nuclear forces exist

Question 11

What is Energy?

Answer 11

The capacity to do work

Question 12

What is a Joule?

Answer 12

1 Joule is the energy transferred in a moving force of 1N through a distance of 1m

Question 13

What is Gravitational Potential?

Answer 13

The capacity for an object to do work as a result of its position in a gravitational field

Question 14

What is Power?

Answer 14

The power generated by a force is the rate at which it does work

Question 15

Power Equation?

Answer 15

Power = Work Done/ TimeP = W/t

Question 16

What is a Watt?

Answer 16

One watt is the power generated when one joule of energy is transferred per second

Question 17

What is Efficiency?

Answer 17

Useful Power Output/ Power Input

Question 18

What is Newton’s First Law? (Law of Inertia)

Answer 18

A body will remain at rest or continue to move at a constant velocity unless acted on by a resultant force

Question 19

What is Inertia?

Answer 19

The resistance a body has to a change in state of motion

Question 20

What is Linear Momentum?

Answer 20

Product of an objects mass and velocity

Question 21

Momentum Equation

Answer 21

Mass x Velocity = Momentum p = mv

Question 22

What is the derivation of the Change in Momentum?

Answer 22

P = mv - mu P/t = (mv - mu)/t = m((V-u)/t)= ma = FThe change in momentum = Force

Question 23

What is Newton’s Second Law?

Answer 23

The rate of change of momentum of an object is directly proportional to the resistant force and takes place in the direction of the force

Question 24

What is Newton’s Third Law?

Answer 24

If body A exerts a force on body B then body B exerts a force in body A that is:• Equal in magnitude • Of the same type• In the opposite direction

Question 25

What is the Impulse?

Answer 25

The product of the magnitude of the force and the length of time it’s appliedThe impulse is equal to the area under the F/t graph

Question 26

What is the Conservation of Momentum?

Answer 26

For a system of interacting objects the total momentum of a specified direction remains constant as long as no external forces act on the system

Question 27

What is an Elastic Collision?

Answer 27

The total kinetic energy and momentum of the system are conserved In an inelastic collision kinetic energy is not conserved whilst momentum is

Question 28

What happens in an Explosion?

Answer 28

In an explosion the vector sum of all the momenta of individual fragments is 0

Question 29

What’s an Oblique Collision?

Answer 29

When two objects of equal mass collide in a non head on elastic collision they will always move away at 90° from each other

Question 30

What is Hooke’s Law?

Answer 30

The force in a solid is proportional to the applied extension within the elastic limit of that solid F = Kx

Question 31

What is the Elastic Limit

Answer 31

The maximum extent to which a solid may be stretched without permanent alteration

Question 32

Elastic Deformation?

Answer 32

Deformation that is fully reversed when the load is removed

Question 33

What is Plastic Deformation?

Answer 33

The permanent deformation result in from tensile stresses exceeding its elastic limit

Question 34

What is Elastic Potential?

Answer 34

When a spring is deformed work is done —> Energy is stored in the deformed material as elastic potential Equal to the work done when producing an extension or compressionE = 1/2Kx^2

Question 35

What is Stress?

Answer 35

The force applied per unit across a cross sectional area = F/A Can be tensile or compressive

Question 36

What is Strain?

Answer 36

The fractional change in length under load= x/L

Question 37

What is Ultimate Tensile Strength?

Answer 37

The maximum stress a material can stand when being stretched before breaking

Question 38

What does bring a Brittle Material mean?

Answer 38

Can with stand large forces whilst experiencing little deformation but will break beyond their elastic limit

Question 39

What does being a Ductile Material mean?

Answer 39

Can be stretched beyond their elastic limit without breaking

Question 40

What is Polymeric Behaviou?

Answer 40

Material made of any smaller molecules bonded together often made of tangled chains. The polymer chains can be unravelled as the rubber is stretched after a point the rubber becomes more still and difficult to extend

Question 41

What is the Young Modulus?

Answer 41

A constant for a given material and is a measure of its stiffness given by the gradient of a stress strain graph Young Modulus = Stress/Strain

Question 42

What is Archimedes’ Principle?

Answer 42

The upthrust exerted on a body immersed in a fluid is equal to the weight of the fluid that the body displaces