force

Question 1

What is a force?

Answer 1

A force is a push or pull

Question 2

How can you measure forces?

Answer 2

with a spring balance

Question 3

What is a magnitude?

Answer 3

The size of a force

Question 4

What is the SI unit of force?

Answer 4

N (Newton)

Question 5

What is frictional force?

Answer 5

Friction is a contact force that opposes motion at the point of contact.

Question 6

How does Friction work?

Answer 6

Objects under a microscope have tiny irregularities that resist motion when interlocked.

Question 7

Advantages of Friction

Answer 7

Grip:
-enables one to walk around without slipping
-enables vehicles to slow down and come to a stop
-enables one to hold a pen and write on a surface
Causes wear and tear:
-friction wielding
Causes heat:
-used by Man to start fires, keep warm
-can be used for processes like friction wielding.

Question 8

Disadvantages of Friction

Answer 8

Grip:
-slows things down like moving cars and airplanes
Causes wear and tear:
-wears out the soles of your shoes, tires
-wears down machines after time
Causes heat:
-increases heat in machinery components
-reduces the efficiency of machines (energy that could have been converted to do useful work is instead converted to unwanted heat energy)

Question 9

how can we reduce friction?

Answer 9

-streamlined shape
-smooth body that reduces water and air resistance
-applying lubricants like grease and oil to the surfaces in contact
-attaching ball bearings to surfaces in contact
-preventing (or reducing contact between two objects

Question 10

how do lubricants work?

Answer 10

Interlocking of irregularities is avoided to a great extent and movement becomes smooth

Question 11

what do maglev trains and hovercrafts have in common?

Answer 11

they both prevent/reduce contact between the other object
a maglev train is levitated above its track by the magnetic force of repulsion between the train and the tracks. this reduces the amount of surface in contact and consequently the frictional force. The train ride is faster, smoother and less noisy
a hovercraft ‘floats’ above water on a cushion of air to reduce friction between the base of the hovercraft and water

Question 12

what is magnetic force?

Answer 12

magnetic force is the force of attraction (pull) or repulsion (push) produced by magnets is known as the magnetic force. magnetic force is a non-contact force.

Question 13

how is magnetic repulsion used?

Answer 13

lift maglev train above tracks

Question 14

how is magnetic attraction used?

Answer 14

a huge magnet is used to separate waste materials in scrap yards that are magnetic (iron and steel) from non-magnetic waste materials and recycle them
can also be used as magnetic seal in refrigerator doors

Question 15

what is gravitational force?

Answer 15

the gravitational force is the force of attraction that pulls all physical objects with mass to the center of a body. it is a non contact force.

Question 16

what is weight?

Answer 16

an object’s weight is the amount of gravitational force acting on it.
changes with gravitational field strength
weight of an object is different on earth and moon
si unit is newton (N)
spring balance is used to measure weight

Question 17

what is mass?

Answer 17

the amount of the matter in a body
does not change with gravitational field strength
mass of an object is the same on earth and moon
si unit is kilogram (kg)
measured with electronic balance or beam balance

Question 18

what is the formula to calculate the weight of an object?

Answer 18

W = m x g
w = weight
m= mass
g= gravitational field strength

Question 19

what can a force do to a physical object?

Answer 19

-change the size/shape of object
-change the state of rest or motion
-change direction of object
-change speed of object

Question 20

explain what a moment is

Answer 20

the turning effect of the force on the body on which it is acting on
- the moment of a force can be clockwise (right) or anti-clockwise (left)

Question 21

what is pressure

Answer 21

pressure is the force acting per unit area
si unit of pressure is pascal

Question 22

how to calculate pressure

Answer 22

P = F/A
P=pressure (Pa)
F=force(N)
A=area of contact (m^2)

Question 23

what is the relation between area and pressure

Answer 23

the smaller the area, the greater the pressure
the larger the area, the smaller the pressure

Question 24

why is there pressure in liquids

Answer 24

weight of water pushes down on the water below
the water pressure depends on the depth of water
the deeper, the more pressure, since there is more water above that have more weight
pressure at the same depth in a liquid acts equally in all directions

Question 25

how do suction caps work?

Answer 25

when you force a suction cup against a surface, most of the air in between the suction cup and the surface is squeezed out

there is a difference in atmospheric pressure between the region inside the suction cup and the atmosphere itself. since the region in the suction cup exerts less pressure than the pressure in the atmosphere. pressure acts in all directions so the atmosphere outside the suction cup is holding it against the surface and the vacuum is unable to counter this amount of pressure.

Question 26

how does a straw a work

Answer 26

there is air in the straw and air on the water that is being pulled down due to atmospheric pressure. when you suck a straw , there is less air pressure in it, so now the only air pushing the water down is the air outside of the straw. this causes liquid to shoot up into the straw

Question 27

how does a syringe work

Answer 27

when the piston is pulled, the pressure within the cylinder of the syringe decreases. the atmospheric pressure acting on the liquid surface pushes the liquid up the needle and into the cylinder