P5-Forces KW

Question 1

Acceleration

Answer 1

The rate of change of velocity. It can be calculated from the gradient of a velocity-time graph.

Question 2

Atmosphere

Answer 2

The thin layer of air surrounding the Earth, which gets less dense with increasing altitude

Question 3

Braking Distance

Answer 3

The distance a vehicle travels under the braking force. This can be affected by adverse road and weather conditions as well as the condition of the vehicle.

Question 4

Centre of Mass

Answer 4

The single point through which the weight of the object can be said to act

Question 5

Changes of Momentum (H)

Answer 5

When a force acts on a moving object, or one an object that has the ability to move, a change of momentum will occur. The force is equal to the rate of change of momentum. (H)

Question 6

Conservation of Momentum (H)

Answer 6

The total momentum of a system before an event is always equal to the total momentum of the system after the event (H)

Question 7

Contact Forces

Answer 7

A force that occurs when objects are physically touching

Question 8

Displacement

Answer 8

A measure of how far an object moves in a given direction. It is the straight line between the starting and finishing points and is a vector quantity.

Question 9

Distance

Answer 9

A measure of how far an object moves, that does not depend on direction and is therefore a scalar quantity.

Question 10

Elastic Deformation:

Answer 10

Non-permanent deformation which allows the object to return to its original shape when the deforming forces are removed.

Question 11

Elastic Limit

Answer 11

The force beyond which an object will no longer deform elastically, and will instead deform plastically.

Question 12

Elastic Potential Energy

Answer 12

The energy stored in a spring when it is stretched or compressed, due to the work done on the spring by the deforming force. It is equal to the work done as long as the object does not plastically deform.

Question 13

Equilibrium

Answer 13

An object is in equilibrium if the resultant force and resultant moment are both equal to zero.

Question 14

Floating (H)

Answer 14

An object will float if the volume of liquid it displaces has a greater weight than that of the object itself. The upthrust acting on the object is greater than its weight. (H)

Question 15

Fluid

Answer 15

A liquid or gas

Question 16

Forces

Answer 16

A push or pull that an object experiences due to the interaction with another object. Force is a vector quantity.

Question 17

Inertia (H)

Answer 17

The tendency of an object to remain in its same state of uniform motion or rest. (H)

Question 18

Inertial Mass (H)

Answer 18

A measure of how hard it is to change an object’s velocity. It is defined as the ratio of force over acceleration. (H)

Question 19

Limit of Proportionality

Answer 19

The point beyond which the extension of an elastic object is no longer directly proportional to the force applied to it.

Question 20

Moment

Answer 20

The turning effect of a force, equal to the product of the magnitude of the force and the perpendicular distance from the pivot to the line of action of the force.

Question 21

Momentum (H)

Answer 21

The product of an object’s mass and velocity (H)

Question 22

Newtonmeter

Answer 22

A calibrated spring-balance used to measure weight

Question 23

Newton’s First Law

Answer 23

If a stationary object’s resultant force is zero, the object will remain stationary. If a moving object’s resultant force is zero, the object will continue to move at the same speed, and in the same direction

Question 24

Newton’s Second Law

Answer 24

An object’s acceleration is directly proportional to the force applied to it, and inversely proportional to its mass

Question 25

Newton’s Third Law

Answer 25

The forces that two objects exert on each other when they interact are equal and opposite

Question 26

Non-Contact Forces

Answer 26

A force that occurs when objects are physically separated

Question 27

Plastic Deformation

Answer 27

Permanent deformation which means the object will no longer return to its original shape when the deforming forces are removed.

Question 28

Resolution of Forces (H)

Answer 28

All forces can be resolved into two perpendicular components that have the same effect as the single force. (H)

Question 28

Pressure in a Column (H)

Answer 28

The pressure in a column of liquid is equal to the product of the liquid’s density, the height of the column and the gravitational field strength. (H)

Question 29

Scalar Quantities

Answer 29

Quantities that only have a magnitude, not a direction.

Question 30

Resultant Moment

Answer 30

The single moment that has the same effect as the sum of all the other clockwise and anticlockwise moments acting on an object

Question 30

Resultant Force

Answer 30

The single force that can replace all the individual forces acting on an object, and have the same effect

Question 31

Sinking (H)

Answer 31

An object will sink if the volume of liquid it displaces has a lower weight than that of the object itself. The upthrust acting on the object is lower than its weight and so there is a resultant downwards force

Question 32

Speed

Answer 32

A scalar quantity that is a measure of the rate of increase of distance.

Question 33

Spring Constant:

Answer 33

A measure of a spring’s stiffness, which is the constant of proportionality for a spring’s extension. The higher the spring constant, the smaller the extension is for a given force.

Question 34

Stopping Distance

Answer 34

The sum of the thinking and braking distances.

Question 35

Thinking Distance

Answer 35

The distance a vehicle travels during the driver’s reaction time. Typical human reaction times are in the range of 0.2-0.9 seconds. This reaction time may be affected by tiredness, drugs or alcohol.

Question 36

Upthrust (H)

Answer 36

The upward force acting on an object in a fluid, due to it experiencing a greater pressure below it than above it. (H)

Question 37

Vector Quantities

Answer 37

Quantities that have both a magnitude and direction. They are represented by an arrow, with the length representing the magnitude and the arrowhead representing the direction.

Question 38

Velocity

Answer 38

A vector quantity that is a measure of the rate of change of displacement. It is the speed in a given direction

Question 39

Weight

Answer 39

The force acting on an object due to gravity. It is equal to the product of the object’s mass and the gravitational field strength at its location.

Question 40

Work Done

Answer 40

Work is done on an object when a force causes it to move through a distance. It is directly proportional to the distance travelled and the magnitude of the force in the direction of motion.