Forces and motion

Question 1

what are the 9 units used in forces and motion?

Answer 1

• kilogram (kg)
• metre (m)
• metre/seconds (m/s)
• metre/seconds 2 (m/s 2)
• newton (N)
• seconds (s)
• newton/kilograms (N/kg)
• newton metre (Nm)
• kilogram metre/ second (kg m/s)

Question 2

where is the distance placed on a distance time graph?

Answer 2

on the y axis (usually in metres)

Question 3

where is the time placed on a distance time graph?

Answer 3

on the x axis (usually in seconds).

Question 4

what does it mean when the line in the distance time graph is flat?

Answer 4

it means the object is stationary.

Question 5

what does the gradient of the line (change in y/ change in x) mean?

Answer 5

speed

Question 6

what is the formula you use to calculate the average speed?

Answer 6

speed (m/s) = distance travelled (m)/ time taken (s)

Question 7

Practical: how to investigating the motion of everyday objects such as toy cars or tennis balls?
(there are 8 points)

Answer 7

• You need a stop watch and metre rule.
• mark the start and end positions (to know the difference).
• use a metre ruler to measure the distance.
• put the toy car on the starting point and release it.
• start the timer and stop it only when the car gets to the end point.
• write down how long it took.
• finally calculate the average speed by using the formula average speed = distance travelled/ time taken.
• repeat experiment more than once.

Question 8

what is the formula for acceleration?

Answer 8

acceleration = final velocity - starting velocity/ elapsed time

Question 9

where does velocity go on a velocity time graph?

Answer 9

on the y axis (usually in m/s)

Question 10

where does time go on a velocity time graph?

Answer 10

on the x axis (usually in s)

Question 11

what does it mean when the line is flat on a velocity time graph?

Answer 11

it means the object is moving at a constant velocity.

Question 12

what is the gradient on a velocity time graph?

Answer 12

it is the acceleration.

Question 13

how do you calculate the distanced travelled on a velocity time graph?

Answer 13

you calculate the area under the line

Question 14

what formula do you use to calculate acceleration from the gradient of a velocity time graph?

Answer 14

gradient = acceleration = change in velocity/ time

Question 15

how to calculate the area under the graph?

Answer 15

It can be calculated as rectangles and triangles.

Question 16

what is the formula that calculates the relationship between final speed, initial speed acceleration and distanced moved?

Answer 16

(final speed) 2 = (initial speed) 2 + (2 x acceleration x distanced moved)

v2 = u2 + (2 x a x s)

key:
v = final speed
u = initial speed
a = acceleration 
s = distanced moved
(word2 = word squared)

Question 17

forces can act on a body to change what 3 things ?

Answer 17

• velocity
• speed
• direction

Question 18

can forces act on the shape of a body?

Answer 18

yes, it can stretch it, squish it and twist it.

Question 19

what are the 9 different types of force?

Answer 19

• gravitational
• weight
• friction
• electrostatic
• air resistance (drag)
• tension (force in a spring)
• up thrust
• lift
• thrust

Question 20

is force a vector?

Answer 20

yes, it has a direction, a push or pull, up, down, left or right.

Question 21

how to calculate a resultant force with lines that go to the same side?

Answer 21

you add them together.
e.g there are 2 arrows in the same side (right) of the car.

one is 30N the other is 60N.

the resulted force will be = 90N to the right

Question 22

how to calculate a resultant force with lines going the opposite side side?

Answer 22

you subtract the forces.
e.g there are town arrows, one in the right side and one in the left side of the car

the left side is 10N and the right side is 30N

you subtract them together (subtract the smaller force from the bigger force), meaning that the resultant force is = 20N to the right (because the right side has a bigger force)

Question 23

how is friction caused?

Answer 23

it is caused by rubbing surfaces.

Question 24

how does friction act?

Answer 24

it acts the opposite direction to motion.

Question 25

what is the formula for the relationship between unbalanced force, mass and acceleration?

Answer 25

force = mass x acceleration

f = m x a

Question 26

what is the formula for the stopping distance?

Answer 26

stopping distance = thinking distance + breaking distance

Question 27

what is the formula for the relationship between weight, mass and gravitational field strength?

Answer 27

weight = mass x gravitational field strength

W = m x g

Question 28

what factors affect Thinking distance?

there are 4

Answer 28

• tiredness
• alcohol
• speed of the car
• drugs

Question 29

what factors affect Braking distance?

there are 5

Answer 29

• road conditions
• tyre conditions
• brake conditions
• speed of the car
• mass of the car

Question 30

what are the forces acting on falling objects? explain what happens when an object falls
(there are 4 point you need to make)

Answer 30

• as the object gains speed, the object’s weight stays the same however, the air resistance increases.
• there is a resultant force acting downwards.
• Eventually the object’s weight will be balanced by air resistance.
• there is no resultant force and the object reaches a steady speed (this is known as thermal velocity).

Question 31

practical/ investigate: how does extension varies with applied force for helical springs, metal wires and rubber bands.
(there are 6 points)

Answer 31

1. measure the length of your spring (without any hanging masses).
2. hang a mass of 100g on the spring.
3. measure the new length of the spring.
4. calculate the extension of the spring.
5. continue increasing the mass, calculating the new length of the spring, and calculating the extension of the spring.
6. take note of your results and put it on a table.

Question 32

what is Hooke’s law?

Answer 32

Hooke’s law states for small deformation of and object, the displacement or size of the deformation is directly proportional to the deforming force or load.

Question 33

what is elastic behaviour?

Answer 33

it is the ability of a material to recover original shape after the force is removed.

In a spring it occurs when the force is lower than the elastic limit.

Question 34

what is elapsed time ?

Answer 34

is the amount of time that passes from the start of an event to its finish