forces

Question 1

what is the difference between a scalar and a vector quantity?

Answer 1

scalar- magnitude only
vector- magnitude and direction

Question 2

give an example of a scalar quantity?

Answer 2

• temperature
• mass
• speed
• pressure
• time

Question 3

give an example of a vector quantity?

Answer 3

• displacement
• velocity
• acceleration
• force
• momentum

Question 4

what is a force?

Answer 4

a push or a pull that acts on an object due to its interaction with another object

Question 5

give examples of contact and non-contact forces?

Answer 5

contact: friction, air resistance, tension

non-contact: gravitational, electrostatic, magnetic force

Question 6

what is weight?

Answer 6

the force acting on an object due to gravity

Question 7

state the equation to calculate weight

Answer 7

weight= mass x gravitational field strength

Question 8

define “centre of mass”

Answer 8

the single point through which the weight of the object can be said to act through

Question 9

how is weight measured?

Answer 9

using a calibrated spring- balance
(newton meter)

Question 10

what is the resultant force?

Answer 10

the singular force that can replace all the individual forces acting on an object

and have the same effect

Question 11

define “work done”

Answer 11

work is done on an object when a force causes it to move through a distance

it is directly proportional to the distance traveled and direction of motion

Question 12

what is velocity

Answer 12

a measure of the rate of change of displacement (speed in a given direction)

Question 13

how does one calculate stopping distance?

Answer 13

sum of the breaking and thinking distance

Question 14

state newton’s first law?

Answer 14

if a stationary object’s resultant force is zero, the object will remain stationary.

if a moving object’s resultant force is zero, the object will continue to move at the same speed, in the same direction

Question 15

define inertia

Answer 15

the tendency of an object to remain in its same state of uniform or rest

Question 16

what is newton’s second law?

Answer 16

an object’s acceleration is directly proportional to the force applied to it, and inversely proportional to its mass

Question 17

what is inertial mass?

Answer 17

a measure of how hard it is for an object to change its velocity

Question 18

explain newton’s third law

Answer 18

the force that two objects exert on each other when interacting are equal and opposite

Question 19

state the law of conservation of momentum

Answer 19

the total momentum of a system before an event is equal to the total momentum after the event

Question 20

an object is in equilibrium if…

Answer 20

the resultant force and the resultant moment are both equal to zero

Question 21

what is the resultant moment?

Answer 21

the single moment that has the same effect as all of the other clockwise and anti-clockwise moments acting on an object

Question 22

what is the moment of a force?

Answer 22

a measure of a force’s tendency to cause a body to rotate

Question 23

what does the gradient of a distance-time graph tell you?

Answer 23

the speed

Question 24

state the equation linking acceleration, changing velocity and time take

Answer 24

acceleration= change in velocity /
time taken

Question 25

what does the gradient of a velocity-time graph tell you?

Answer 25

acceleration

Question 26

what does the area under a velocity-time graph equate to?

Answer 26

the distance travelled by the object

Question 27

define terminal velocity

Answer 27

the maximum velocity an object can reach when falling through a fluid

Question 28

explain what happen to an object as it reaches terminal velocity

Answer 28

- object initially accelerates due to the force of gravity - resistance from the fluid increases, balancing out the force of gravity - the resultant force becomes zero and terminal velocity is reached

Question 29

resultant force equals…

Answer 29

mass x acceleration

Question 30

how is inertial mass defined?

Answer 30

the ratio of force over acceleration

Question 31

describe the changing motion of a skydiver, in terms of forces

Answer 31

- initially, air resistance is less than gravity so skydiver accelerates - acceleration causes air resistance to increase - resultant force becomes zero - skydiver reaches terminal velocity

Question 32

what does pressure in a column equal to?

Answer 32

the product of the liquid’s density, height of the column, and the gravitational field strength

Question 33

define upthrust

Answer 33

the upward force acting on an object in a fluid due to it experiencing a greater pressure below than above

Question 34

what creates atmospheric pressure?

Answer 34

air molecules colliding with a surface

Question 35

explain why atmospheric pressure decreases with increasing altitude

Answer 35

- air molecules colliding with a surface create pressure - as altitude increases, distance between molecules increases - so fewer collisions with a surface occur

Question 36

why does pressure on a swimmer increase with depth?

Answer 36

- increasing depth increases the volume of water above swimmer - increases the weight acting on the swimmer

Question 37

what is the difference between distance and displacement?

Answer 37

distance is a scalar quantity displacement is a vector quantity

Question 38

what is meant by braking distance?

Answer 38

distance travelled by a vehicle under the breaking force

Question 39

what is acceleration?

Answer 39

the rate of change of velocity

Question 40

breaking distance can be affected by…

Answer 40

- wet or icy weather - adverse road conditions - poor condition of vehicle’s tires or breaks

Question 41

what could large decelerations lead to?

Answer 41

breaks overheating and loss of control

Question 42

what happens when a force is applied to the breaks of vehicle?

Answer 42

- work done by the friction force between the breaks and the wheel, reduces kinetic energy of the vehicle - temperature of the breaks increases

Question 43

state the equation for momentum

Answer 43

momentum = mass x velocity

Question 44

when does a change in momentum occur?

Answer 44

when a force acts on an object that is moving, or able to move

Question 45

describe an investigation to determine spring constant

Answer 45

- set up apparatus with spring hanging from a clamp on a clamp-stand, with a ruler clamped beside it - record the position of the bottom of the spring on the ruler (equilibrium position) - hang a 1N weight from the spring - measure the extension - add another 1N weight and measure the new extension - continue in this manner until 10N weights are added

Question 46

write down the equation that links extension, force, and spring constant

Answer 46

force = extension x spring constant