forces and motion

Question 1

what is meant by a scalar quantity

Give 2 examples

Answer 1

a scalar quantity is a magnitude. it can be described fully with a single numerical value

Ex: speed, time, mass, energy

Question 2

what is meant by a vector quantity

Give 2 examples

Answer 2

a vector quantity has both a magnitude and a direction

Ex: force, velocity, displacement, momentum

Question 3

which property of a distance time graph can be used to calculate speed?

Answer 3

Gradient (or slope)

Question 4

state an equation linking distance moved, time taken and average speed with their respective units

Answer 4

average speed(m/s) = distance(m) / time(s)
v=d/t

Question 5

what is meant by acceleration

give its units

Answer 5

acceleration is the change in velocity per unit of time

m/s*2

Question 6

state an equation linking acceleration, change in velocity and time taken

Answer 6

acceleration = (change in velocity)/time
a = (v-u)/t

Question 7

which property of a velocity-time graph can be used to calculate the acceleration

Answer 7

gradient (slope)

Question 8

which property of a velocity-time graph can be used to calculate distance travelled

Answer 8

area under the graph

Question 9

state an equation linking final speed, initial speed, acceleration and distance travelled

Answer 9

v2 = u2 + 2as

*2 means squared

Question 10

name two types of forces that always opposes motion

Answer 10

1. friction

2. air resistance (drag)

Question 11

a) which type of force holds the planets around the sun

b) which type of force holds electrons around nucleus

Answer 11

A) gravitational force

B) electrostatic force

Question 12

state the ways that a force can affect the object that it is being applied on

Answer 12

• it can change the shape of the object (extension/compression)
• it can change the speed of the object
• it can change the direction the object is moving

Question 13

state the equation linking force, mass and acceleration

Answer 13

force (N) = mass(kg) x acceleration (m/s*2)

F = m x a

Question 14

state the equation linking mass, weight and

Answer 14

weight(N) = mass(kg) x g (m/s*2)
W = mg

Question 15

what is the relationship between stopping distance, braking distance and thinking distance of a car while stopping

Answer 15

stopping dist. = thinking dist. + braking dist.

Question 16

state 4 factors that affect the stopping distance of a car

Answer 16

• reaction time
• initial speed
• road conditions
• tire conditions
• weather conditions
• driver’s conditions
• mass of car

Question 17

state two factors that affect the air resistance acting on a falling object

Answer 17

• surface area

- speed

Question 18

describe how a falling object reaches to terminal velocity

Answer 18

at first object falls under the effect of its weight accelerating with g. As it accelerates, air resistance opposing the motion increases therefore resultant force acting on the object decreases as F=ma, acceleration decreases

when air resistance becomes equal to weight, forces are balanced so resultant force=0 therefore a=0 and object reaches to terminal velocity

Question 19

state what is meant by obeying Hooke’s law

Answer 19

extension is directly proportional with force applied

Question 20

explain what is the difference between elastic and plastic behaviour

Answer 20

in elastic behaviour, object recovers its original shape when the forces causing the extension is removed

in plastic behaviour, there is a permanent deformation to the shape of the object when forces are removed