Mechanics

Question 1

projectile motion

Answer 1

_ decelerates until max height, vertical velocity = 0, then accelerates downwards. produces a parabolic path (gravity opposes motion) horizontal velocity is constant

Question 2

Vector addition

Answer 2

Vectors are added head to tail

Question 3

Vector Subtraction

Answer 3

The reverse vector is added head to tail (the same but in opposite direction to the original vector).

Question 4

acceleration in circular motion

Answer 4

the speed is not changing, but as the direction of the velocity is changing, the velocity is changing. This leads to acceleration.

Question 5

equilibrium rule (torques)

Answer 5

clockwise torques = anticlockwise torques

Question 6

equilibrium rule (forces)

Answer 6

sum of forces = zero

Question 7

assumptions (momentum)

Answer 7

momentum is conserved, so no external forces are acting

Question 8

what is impulse?

Answer 8

change in momentum

Question 9

conservation of energy

Answer 9

Ep = Ek (no energy is lost)

Question 10

to reach larger acceleration

Answer 10

less mass

Question 11

to reach more kinetic energy

Answer 11

increase force

Question 12

reduction in spring constant

Answer 12

results in increased extension and reduced force.

Question 13

how to reduce spring constant

Answer 13

adding length to springs

Question 14

hookes law

Answer 14

F = kx

Question 15

torque question

Answer 15

F1=ma F2=ma
τ1 = Fd τ2 = Fd = _ Nm-1
Force A = torque / length of object (about cw/ac)
FA = _ N
FB = sum of downwards forces - FA

Question 16

using conservation of momentum (collision)

Answer 16

mv> = (m)v combined
=v combined

Question 17

slippery floor

Answer 17

less friction, no force/decreased centripetal force if circular motion - object moves off tangentially to the circle (direction will change due to unbalanced forces)

Question 18

springs compressing

Answer 18

increase time taken for force to impact, decreasing force. & absorbs energy transmitted over larger time

Question 19

motion, larger degree of parabolic jump

Answer 19

same starting point, higher peak, further end, peak further to right

Question 20

centripetal acceleration

Answer 20

unbalanced force caused by friction leads to inward acceleration

Question 21

springs centripetal force

Answer 21

provided by tension in spring, tension perpendicular to velocity, keeps object moving in a circle at constant speed (which makes object change direction towards centre)

Question 22

centripetal force & velocity

Answer 22

force does not change size of velocity, only changes the direction, force is acting at 90º to direction of velocity.

Question 23

upwards force

Answer 23

reaction

Question 24

downwards force

Answer 24

weight

Question 25

vectors form closed triangle

Answer 25

net force is zero

Question 26

object moves from support A -> B (torques)

Answer 26

force @ support A decreases as force @ support B increases as anticlockwise torque about A increases, if force on B increases, force on A reduces to that net force = 0

Question 27

why do u pull hand back to catch

Answer 27

to remove the objects velocity, exerting force in opposite direction to velocity. force person delivers depends on momentum change required. if time to deliver impulse (by pulling hand backwards) is sufficiently long, force exerted on balloon will be sufficiently reduced.

Question 28

force assumptions

Answer 28

all energy is transferred, no external forces are acting

Question 29

increasing launch speed

Answer 29

increase force pulling - increases stored energy to be converted to kinetic energy (increasing velocity) decrease mass of object - same force produces larger acceleration (over same distance) to produce greater velocity

Question 30

reducing spring constant

Answer 30

changing material of springs, adding length to existing springs. reducing spring constant = increased extension and reduced force.

Question 31

cutesy reminders <3

Answer 31

READ THE QUESTIONS CONVERT TO PROPER UNITS !!!!!!

Question 32

relative speed

Answer 32

add opposing velocities

Question 33

decreasing gravity

Answer 33

decreasing acceleration (due to gravity) increases time in air, increases horizontal distance

Question 34

torque assumption

Answer 34

the bench/bridge is uniform

Question 35

energy assumption

Answer 35

all energy is transferred

Question 36

friction force required to keep object stationary

Answer 36

force on object (ma) x sin 0

Question 37

convert kmh to ms

Answer 37

divide kmh unit by 3.6 :)

Question 38

vector triangle (on hill)

Answer 38

weight, reaction, friction

Question 39

impulse reminder

Answer 39

momentum is constant

Question 40

finding momentum in impulse

Answer 40

add velocities to find change in momentum

Question 41

adding protection (impulse)

Answer 41

force decreased as it is spread over larger time, less likely to injure. momentum remains constant, protection absorbs energy, increases time of collision