P1 Motion

Question 1

state an apparatus used to measure very small distance

Answer 1

micrometer screw gauge

Question 2

apparatus used to measure time (2)

Answer 2

1. stopwatch
2. clock

Question 3

how to measure an interval of time

Answer 3

measure multiple times of one interval and find the mean

Question 4

define speed

Answer 4

the rate of change of position in any directions

total distance / total time

Question 5

define velocity

Answer 5

the rate of change of position in fixed position

total displacement / total time

Question 6

define acceleration (m/s^2)

Answer 6

increase in velocity

change of velocity / total time

Question 7

acceleration of free fall g for a body near to the earth is __

Answer 7

constant

Question 8

define mass

Answer 8

measure of quantity of matter in the substance (kg)

Question 9

define weight

Answer 9

the measure of the gravitational force of the object (N)

w = mg
weight = mass * gravitational force
g = 10N/kg always

Question 10

state the source of gravitational field

Answer 10

the earth

Question 11

state that weight can be compared using a ___

Answer 11

balance

Question 12

define density

Answer 12

measurement of how tightly a material is packed

p = m/v
density = mass / volume

kg/m^3

Question 13

how do you measure a density of an irregular shape (mass is given)

Answer 13

measure the volume by using measure cylinder and water, and divide the mass by the obtained volume

Question 14

forces can change (3) of a body

Answer 14

1. size
2. shape
3. motion

Question 15

define hooke’s law

Answer 15

a law stating that the tightness in a solid is proportional to the applied stress within the elastic limit of that solid.

k = fx
spring constant = force * extension

N/m

Question 16

define elastic limit

Answer 16

point on the graph (extension - load graph) when proportionality is no longer obeyed.

Question 17

define force

Answer 17

F = ma
force = mass * acceleration

N

Question 18

define friction

Answer 18

force between two surfaces which slow down and results in heating

Question 19

example of friction

Answer 19

air resistance

Question 20

what happens when there is no resultant force on a body (2)

Answer 20

1. either remains at rest
   or
2. continues at constant speed in a straight line

Question 21

define moment of a force

Answer 21

turning force around a fixed pivot
eg. opening a door, seesaw

m = fd
moment of force = force * perpendicular distance from the pivot

Question 22

when there is no resultant force and no resultant turning effect, the system is ___

Answer 22

equilibrium

Question 23

define centre of mass

Answer 23

the point on the body with the whole of the mass of the body is assumed to be concentrated at

Question 24

how do you find out the centre of mass of a lamina

Answer 24

• hang up the lamina and hang a string with a force applied to it
• mark the point where the string passes through
• repeat it
• find the point where two or more strings meet
• that is the centre of mass of the lamina

Question 25

describe how the position of centre of mass effects the stability of the material

Answer 25

If the centre of mass is below the point of suspension of an object, it will be in stable equilibrium (e.g. a hanging plant pot). If the centre of mass is above the point of suspension of an object, it will be in unstable equilibrium (e.g. a pencil placed on its sharp end).

Question 26

define pressure

Answer 26

ratio of force to the area

p = f/a
pressure = force / area

Pa N/m^2