Forces And Motion

Question 1

3 things a force can do to an object

Answer 1

Change its shape
Change its velocity
Change its direction

Question 2

What should a force description include

Answer 2

• magnitude
• direction
• object which the force acts on
• object that exerts the force
• nature of the force

Question 3

Normal force

Answer 3

If an object is at rest on a surface, the surface exerts a force on the object. This force is experienced at right angles to the surface

Question 4

Friction

Answer 4

A box on a slop will stay stationary so long as the gradient doesn’t get too high. This is because a force acts on the box up the slope which counteracts the component of weight down the slope

Question 5

Air resistance

Answer 5

This is an example of viscous drag and as with friction it opposes relative motion between the object and the fluid acting when the object is stationary and increases with surface area of the object and density of the fluid

Question 6

Mass

Answer 6

The amount of matter contained in an object, no matter where the object is it mass will be the same

Question 7

Weight

Answer 7

This is the force acting on an object due to its gravitational field (N).

Question 8

Weight =

Answer 8

Mass x g

Question 9

Are forces vectors or scalars?

Answer 9

Vectors

Question 10

Newton’s first law

Answer 10

Constant speed means the forces are balanced or zero resultant force

if a body is at rest or moving at a constant speed in a straight line, it will remain at rest or keep moving in a straight line at constant speed unless it is acted upon by a force.

Question 11

Newton’s second law

Answer 11

The rate of change of momentum of an object is proportional to the resultant force acting on it, and takes place in the direction of that force

Question 12

F=

Answer 12

Mass x area

Ma

Question 13

Newton’s third law

Answer 13

If body A exerts a force on body B, then body B exerts an equal and opposite force on body A

Question 14

Terminal velocity occurs if

Answer 14

there is no air resistance. all objects fall at the same rate

Question 15

Gravitational field strength

Answer 15

The force experienced per unit mass placed in the field

Question 16

Gravitational field strength units

Answer 16

ms-1 or Nkg-1

Question 17

Terminal velocity

Answer 17

The constant, maximum velocity of an object when the resistive forces on it are equal and opposite to the accelerating force

Question 18

Moments

Answer 18

Turning effect of a force and is defined by its equation

Question 19

Moment unit

Answer 19

Nm

Question 20

Moment =

Answer 20

Force x perpendicular distance from pivot

Question 21

Centre of mass/ gravity

Answer 21

A point from which the weight of a body or system may be considered to act

Question 22

Principle of moments

Answer 22

For a system to be in equilibrium:

the total clockwise moment about a point = the total anticlockwise moment about a point provided no external forces act

Question 23

Are moments vector or scalar?

Answer 23

Vecotr

Question 24

Density

Answer 24

A property of the material, it gives the concentration of its mass per unit volume

Question 25

Density =

Answer 25

Mass/volume

Question 26

Density units

Answer 26

kgm-3

Question 27

Pressure

Answer 27

The force per unit area

Question 28

Pressure units

Answer 28

Pa or N/m2

Question 29

Pressure =

Answer 29

Force/area

Density x g x height

Question 30

Archimedes principle

Answer 30

The upthrust exerted on a body immersed in a fluid, whether fully or partially submerged, is equal to the weight of the fluid that the body displaces