motion, forces and energy

Question 1

what is a vector

Answer 1

measurment of displacement

Question 1

what is scalar

Answer 1

dont consider direction, only distance

Question 2

formula for velocity

Answer 2

v=s/t

Question 3

what is velocity?

Answer 3

speed in a given direction

Question 4

formula of speed

Answer 4

s=d/t

Question 5

acceleration of free fall g for
an object near to the surface of the Earth is

Answer 5

approximately constant and is approximately
9.8m/s2

Question 6

what is acceleration

Answer 6

a= change in velocity/ time taken

Question 7

speed time graphs: a flat horizontal line at zero speed =

Answer 7

stationary

Question 8

speed time graph: a flat horizontal line above zero speed

Answer 8

constant speed

Question 9

speed time graphs: an upward sloping line =

Answer 9

accelerating; the steeper the gradient, the higher the acceleration

Question 10

speed time graphs: a downward sloping line =

Answer 10

decelerating.

Question 11

what is terminal velocity

Answer 11

the top speed of any object enperiencing air resistance or any similar friction force

Question 12

what is mass

Answer 12

a measure of the quantity
of matter in an object at rest relative to the
observer

Question 13

what is weight

Answer 13

t weight is a gravitational force on an
object that has mass

Question 14

what is gravitational force

Answer 14

force per
unit mass
g = weight/mass
and know that this is equivalent to the
acceleration of free fall

Question 15

what is density

Answer 15

mass per unit of volume
p= m/ v

Question 16

how to measure irregular shapes

Answer 16

add the irregular shap to water and measure the loss of water. this will be the volume of the object. use the formula p=m/v to calculate the density

Question 17

when will an object float

Answer 17

when it is less than 1g/cm3- or a density less than the liquid it is fut in

Question 18

forces can change the ……. of an object

Answer 18

change its shape
change its size
change its velocity
change its direction of motion

Question 19

what the formula of force

Answer 19

force (N)F=mass (kg) × acceleration (m/s2)=ma

Question 20

what happens when force moves in a circular motion

Answer 20

force is pointed to the centre of the circle

Question 21

what is resultant force

Answer 21

the net force: delta of 2 forces

Question 22

what is force formula for stretching

Answer 22

f= spring constant x extension
k=force/x

Question 23

what is limit of porportionality

Answer 23

the limit of force a spring can take before it doesnt go back to its original way

Question 24

motion in a circular path
due to a force perpendicular to the motion as:

Answer 24

(a) speed increases if force increases, with mass
and radius constant
(b) radius decreases if force increases, with mass
and speed constant
(c) an increased mass requires an increased force
to keep speed and radius constant

Question 25

what is solid friction

Answer 25

force between two
surfaces that may impede motion and produce
heating

Question 26

what is the moment of a force

Answer 26

measure of
its turning effect
examples: opening a lid jar
moment= force x perpendicular distance from the pivot

Question 27

when is an object at equilibrium

Answer 27

when there is no resultant force

Question 28

what is the centre of gravity

Answer 28

It is the average position of all the mass in that object

Question 29

how to determaine the centre of gravity of a irregular shaped plane

Answer 29

1) Cut out an irregular shape of card.
Make a hole near the edge of the shape and place a pin through it.
2) Clamp the pin so that it is horizontal, and make sure the card can rotate.
3) Tie a mass suspended by cotton from the pin. This must be free to swing backwards and forwards like a pendulum.
4) Once the cotton and card have stopped moving, carefully mark where the cotton is aligned on the card by drawing a line along its length (shown as a black solid line in Figure 2).
5) Repeat this procedure for three different positions
the centre of gravity will be where the point intercect

Question 30

what is momentum

Answer 30

mass x velocity

Question 31

what is impulse

Answer 31

force x time

Question 32

conservation of momentum

Answer 32

In any collision, the total momentum before and after the collision is the same

Question 33

what is the resultant force in momentum

Answer 33

change in
momentum per unit time; r
F = ∆p/
∆t