force and motion (required practicals)

Question 1

how do you investigate the link between force and extension? (required practical)

Answer 1

1. set up a stand with a clamp at the top holding a spring and a ruler.
2. measure the length of the spring under no force.
3. add a mass to the spring and measure the new length. the extension is the change in length
4. increase the mass until you have at least 6 measurements.
5. plot a force extension graph. there will be a curve if you exceed the limit of proportionality

Question 2

what is the formula for energy using the spring constant?

Answer 2

energy jules = 1/2 x spring constant N/m x extension² metres

Question 3

what is acceleration?

Answer 3

the change in speed over a certain time.

Question 4

what is the formula for acceleration?

Answer 4

acceleration m/s² = change in velocity m/s ÷ time s

Question 5

what is deceleration?

Answer 5

negative acceleration.

Question 6

what is uniform acceleration?

Answer 6

accelerating at a constant rate.

Question 7

what is the formula for uniform acceleration?

Answer 7

final velocity² m/s - initial velocity² m/s = 2 x acceleration m/s² x distance m

Question 8

what does a distance time graph show?

Answer 8

the distance something travels over time.

Question 9

what does a velocity time graph show?

Answer 9

the velocity of something over time.

Question 10

what does the area under a velocity time graph show?

Answer 10

distance travelled.

Question 11

what is friction?

Answer 11

a force between 2 surfaces that resists motion. it is opposite to movement

Question 12

what is drag?

Answer 12

resistance you get in a fluid. gas or liquid

Question 13

how can you reduce drag?

Answer 13

streamlining. allow fluid to flow easily across something

Question 14

what is terminal velocity?

Answer 14

the maximum velocity something can reach falling through a fluid. accelerating force is equal to the frictional force

Question 15

what changes an objects terminal velocity?

Answer 15

drag.
weight.

Question 16

what is newtons first law of motion?

Answer 16

a resultant force is needed to make something start moving speed up or slow down.

Question 17

what is the formula for resultant force using mass?

Answer 17

resultant force newtons = mass kg x acceleration m/s²

Question 18

what is newtons second law of motion?

Answer 18

the acceleration of an object is directly proportional to the resultant force acting on it. F = MA

Question 19

what is newtons third law of motion?

Answer 19

every action has an equal and opposite reaction. when 2 objects interact the forces they exert on each other are equal and opposite

Question 20

what is inertia?

Answer 20

the tendency for an object to stay in its current state of motion.
until acted on by a resultant force an object at rest will stay in rest and an object at a steady speed will stay at that speed

Question 21

how do you investigate the link between force and acceleration? (required practical)

Answer 21

1. set up a trolley which holds a piece of card with a gap in the middle.
2. set up a light gate on a stand so the trolley and card can pass through the gate.
3. attach a piece of string to the trolley that moves over a pulley with masses attached to the end. the masses provide accelerating force
4. mark a starting line on the surface the trolley is on.
5. put the trolley on the starting line and let go. so the trolley gets pulled off the surface
6. record the acceleration from the light gate.
7. repeat the test twice more to get an average acceleration.
   force = mass of weights x acceleration

Question 22

what is stopping distance?

Answer 22

the total distance a vehicle travels from the driver noticing a hazard to the vehicle being completely stopped.

Question 23

what is the formula for stopping distance?

Answer 23

stopping distance = thinking distance + braking distance

Question 24

what is thinking distance?

Answer 24

how far the vehicle travels during the drivers reaction time.

Question 25

what effects thinking distance?

Answer 25

speed.
reaction time.

Question 26

what effect braking distance?

Answer 26

speed.
weather.
tyre condition.
how good your brakes are.

Question 27

how does braking work?

Answer 27

pushing the brake pedal presses the brakes against the wheel which causes friction. kinetic energy is transferred the thermal energy

Question 28

what is reaction time?

Answer 28

how long it takes someone to respond to something. average is 0.2s - 0.9s

Question 29

what effects reaction time?

Answer 29

tiredness.
drugs.
alcohol.
distractions.

Question 30

what are the 3 typical stopping distances at what speeds?

Answer 30

23m at 30mph.
53m at 50mph.
96m at 70mph.

Question 31

what is momentum?

Answer 31

a combination of mass and velocity.

Question 32

what is the formula for momentum?

Answer 32

momentum kg m/s = mass kg x velocity m/s

Question 33

how does momentum change before and after an event? e.g. collision

Answer 33

momentum before = momentum after.

Question 34

what is the formula for force using momentum?

Answer 34

force N = change in momentum kg m/s ÷ change in time s
change in momentum is also written as mass x change in velocity

Question 35

how is the force experienced in a car crash decreased? with examples

Answer 35

by increasing the time someone slows down for. F = mΔv ÷ Δt
seatbelts stretch slightly.
crumple zones crumple on impact.
air bags slow you down more gradually than the dashboard.