Forces

Question 1

Contact force

Answer 1

the force acting when two interacting object have physical contact with each other

EXAMPLES
- frictional force
- applied force
- normal contact force
- elastic force
- viscous force

Question 2

Non contact force

Answer 2

the force acting over a distance without physical contact between two interacting object

EXAMPLE
- gravitational force
- magnetic force
- electric force

Question 3

Effects of force

Answer 3

• start a motion
• stops a motion
• change the speed of the motion
• change the direction of motion
• changing the shape
• changing the size
• turining an object
• exerting pressure on surfaces

Question 4

Measurement of force

Answer 4

• force is measured in newtons
• meausured by extension spring balance or compression spring balance

Question 5

Normal contact force

Answer 5

• equal magnitude as the weight
• acts in the opposite direction of weight

Question 6

Why is a (book) stationary - normal contact force

Answer 6

the normal contact force on the book acts perpendicularly to the surface of contact between the book and the table. It prevents the book from falling to the ground because of its weight

Question 7

Frictional force

Answer 7

Friction is the contact force that acts between two surfaces in contact with each other that opposes or tends to oppose or resist motion. it usually acts opposite to the direction of motion at the point of contact

Question 8

Viscous Force

Answer 8

• air resistance or water resistence
• friction depends on the surface but air resistance depends on the speed and surface area

Question 9

Gravitational force

Answer 9

• otherwise known as weight
  w = mg

Question 10

Mass

Answer 10

• the measure of the amount of substance ina body
• scalar
• kg
• measure by beam balance
• does not vary
• does not depend on gravitational field strength

Question 11

Weight

Answer 11

• gravitational force exerted by earth on a body placed on earth
• vector
• newtons
• varies
• calibrated spring balance
• depends on the gravitational field strength

Question 12

electric force

Answer 12

• exists between charges

Question 13

magnetic force

Answer 13

• ## force exerted by a magnet or a magnetic material

Question 14

Newton’s first law of motion

Answer 14

• a body will remain in its state of rest or uniform motion in a straight line unless acted upon by a resultant force

Question 15

inertia deifintion

Answer 15

• refers to the reluctance of a body to reluct a change in the state of rest or motion of the body

Question 16

Comparison question

Answer 16

• A is more massive
• a more massive body has a greater reluctance to reluct changes in motion

Question 17

Table question

Answer 17

all masses have inertia. all the objects have inertia and are initially at rest.hence when the objects are subjected to a sudden force , they will tend to stay at rest.

Question 18

Large vehicles

Answer 18

• have greater inertia, more difficult to stop the motion of the vehicle

Question 19

Balanced forces

Answer 19

when there are two forces of equal magnitude acting on the object in opposite direction,they cancel out each other, and there is a net force of zero and no change in motion.

Question 20

Unbalanced forces

Answer 20

• if the forces acting on the object do not cancel out each other, there is a rsultant force and a net force of not zero, causing a change in motion.

Question 21

Forces acting on object

Answer 21

• when two forces are acting on the object in the same dircetion, the net force is the sum of the two forces( they share the same line of action)
• when two unequal forces are acting on the same object but in different direction, the net force is the difference between the forces.

Question 22

Pressure

Answer 22

Pressure = force/ area

Amount of force acting perpendicularly on a unit area

Question 23

Atmospheric pressure

Answer 23

• air moloecules around us move with high velocity
• when they collide with surfaces, they exert a force
• the pressure exerted by air in the earth’s atmosphere on objects exposed to air

Question 24

Straw theory

Answer 24

• when the straw is sucked, the air pressure in the straw decreases
• the atmospheric pressure acting on the water is larger than the air pressure in straw.
• a net force is exerted on the surface which causes the fluid to enter the straw

Question 25

Balloon theory

Answer 25

as the balloon rises into the air, the atmospheric pressure acting on the balloon from the outside is smaller than the air pressure inside.
- there is a net fore that pushes on the balloon from inside causing it to expand.

Question 26

squash theory

Answer 26

the blood in our body exerts a larger pressure than the air. hence there is a net force acting from insdie our body, preventig from benig squashed