CH3: Force and Pressure

Question 1

definition of contact force

Answer 1

a force that exits between objects that are in contact.

Question 2

examples of contact force

Answer 2

friction, air resistance, normal force, tension

Question 3

definition of non-contact force

Answer 3

a force that does not require objects to be in contact to exist.

Question 4

examples of non-contact force

Answer 4

gravitational force, magnetic force, electrostatic force

Question 5

definition of mass

Answer 5

a measure of the amount of matter in a body

Question 6

instrument to measure mass

Answer 6

beam balance

Question 7

definition of gravitational field

Answer 7

a region in which a mass experiences a force due to gravitational attraction

Question 8

definition of gravitational field strength

Answer 8

gravitational force per unit mass placed at a point

Question 9

formula of gravitational field strength

Answer 9

w=mg

Question 10

what is the relationship between the gravitational field strength and the distance from earth?

Answer 10

gravitational field strength is strongest on its surface and decreases as you go further away from earth.

Question 11

what is the acceleration of free fall near the earth?

Answer 11

10 m/s^2

Question 12

definition of weight

Answer 12

gravitational force acting on an object that has mass

Question 13

instrument to measure weight

Answer 13

spring balance, newton meter

Question 14

what are the differences between mass and weight?

Answer 14

mass: scalar quantity, kilogram, independent of gravitational field strength, measured with a beam balance, amount of matter
weight: vector quantity, newton, dependant on gravitational field strength, measured with a spring balance

Question 15

definition of density

Answer 15

mass per unit volume

Question 16

formula of density

Answer 16

P=m/v (P is rho)
SI unit: kg/m^3

Question 17

what happens when an object of 5kg/m^3 is cut into 3 equal parts? state the density and explain your answer.

Answer 17

each part will be 5 kg/m^3. The density remains the same as they are made of the same substance which has a constant value of density.

Question 18

definition of pressure

Answer 18

force acting per unit area

Question 19

formula of pressure

Answer 19

P=F/A
SI unit= N/m^2 or Pascal (Pa)

Question 20

what is the relationship between force and area in terms of pressure?

Answer 20

the bigger the area, the smaller the force, the smaller the pressure and vice versa