2nd half Forces and Motions

Question 1

What is the SI unit for mass?

Answer 1

Kg

Question 2

What is the SI unit for distance?

Answer 2

M

Question 3

What is the SI unit for speed?

Answer 3

m/s

Question 4

What is the SI unit for acceleration?

Answer 4

m/s2

Question 5

What is the SI unit for force?

Answer 5

N

Question 6

What is the SI unit for time?

Answer 6

s

Question 7

What is the SI unit for gravitational force constant?

Answer 7

g

Question 8

What is the SI unit for spring constant?

Answer 8

k

Question 9

What is newtons 2nd law?

Answer 9

zero resultant force means an object is either stationary or remains at a constant velocity, if there is a resultant force then the object accelerates.

Question 10

What is the difference between weight and mass?

Answer 10

Mass is how much matter you are made of and doesn’t change whereas weight is a force that acts upon mass.

Question 11

state the equation that uses weight, mass and gravitational force constant.

Answer 11

weight = mass x gravitational force constant

or w=mg

Question 12

What is the gravitational force constant on earth?

Answer 12

10 N/Kg

Question 13

On Earth when there is no drag how do things fall towards earth?

Answer 13

The acceleration of freefall which is 10m/s2

Question 14

What act to oppose the direction of motion?

Answer 14

Friction and drag

Question 15

Drag ________ as velocity ____________.

Answer 15

Increases, increases

Question 16

Drag ___________ as surface area (perpendicular to velocity) ___________

Answer 16

Increases, increases

Question 17

State the equation that uses force, mass and acceleration.

Answer 17

Force = mass x acceleration

Where f is the resultant force

Question 18

Describe in terms of individual forces and resultant force why falling objects reach terminal velocity.

Answer 18

Object falls because weight is pulling it down
Tiny bit of drag but resultant force downward
Because there is a resultant force it accelerates
As it accelerates drag increases until it is equal and the resultant force is zero
Zero resultant force means no acceleration but constant velocity

Question 19

Describe an experiment to investigate the force on falling objects

Answer 19

Measure time taken for empty cupcake case to fall from window
Need timer and scale
Drop case and measure time it takes to drop
Work out velocity
To improve drop from higher place or make sure no wind

Question 20

How do you calculate the linear momentum of an object from its mass and velocity?

Answer 20

Momentum = mass x velocity

= kgm/s

Question 21

How do you calculate the change in momentum for an object that changes velocity?

Answer 21

Work out the initial and final momentum and find the difference.

Question 22

What is the equation for the principle of the conservation of momentum to objects that collide in order to calculate final mass, velocity or momentum?

Answer 22

Final momentum = initial momentum

for sticky collisions, springy collisions and explosions

Question 23

What is the equation that states the force is the equal to the change of momentum?

Answer 23

Force = change in momentum/time taken

= final momentum - initial momentum/time taken

Question 24

Using the equation that states the force is equal to the rate of change in momentum explain how safety features like crumple zones, airbags and seat belts save lives.

Answer 24

force = rate of change in momentum
For same velocity momentum change is the same, crumple zones increase the time of collision 
force = change in momentum
            / time
This reduces force

Question 25

State and describe the meaning of the equation that uses stopping distance, thinking distance and braking distance

Answer 25

Stopping distance = thinking distance + braking distance
If a rabbit jumped out on road, you process the thought of braking and you travel a distance while doing so = thinking distance
You press the break and the car takes time to slow down = braking distance
These add up to the overall stopping distance

Question 26

Describe factors that affect thinking distance, braking distance or both

Answer 26

Thinking - Poor visibility, drunk

Braking - Bad road conditions

Question 27

Where does the weight of a body act?

Answer 27

Through its centre of gravity

Question 28

State the formula for a moment

Answer 28

force of moment = force x distance from pivot

Question 29

State the principal of moments

Answer 29

For an object at equilibrium, the sum if the clockwise moments are equal to the sum of the anticlockwise moments

Question 30

Explain how forces act on a beam supported at either end on a pivot

Answer 30

They vary with the placement of the load by applying the principle of moments to each of the pivots

Question 31

Describe an experiment to investigate how extension varies for springs, wires and rubber bands

Answer 31

Hang a spring from a clamp and add weight of 100g measuring the distance each time from the top of the spring to the top of the masses

Question 32

State Hooke’s Law

Answer 32

Extension is proportional to the force applied
F=fx
k= spring constant
x= extension

Question 33

Hooke’s law only applies to what?

Answer 33

The linear region of the graph, where force is directly proportional to extension

Question 34

What is it called when a spring can stretch no more?

Answer 34

The elastic limit or the limit of proportionality

Question 35

Describe elastic behaviour.

Answer 35

The ability of a material to recover its original shape after the force has been removed.

Question 36

Describe plastic deformation.

Answer 36

The permanent altering of the shape of a material/body