section 3 - mechanics

Question 1

what is a moment?

Answer 1

force x perpendicular direction from axis to line of action of force.

Question 2

momentum equation?

Answer 2

mass x change in velocity.

Question 3

state newton’s first law.

Answer 3

an object remains and rest or in constant motion unless acted on by a resultant force.

Question 4

state newtons second law.

Answer 4

F = ma (the resultant force is proportional to the rate of change of momentum)

Question 5

what is an alternate form of momentum equation?

Answer 5

F = ma (ma = momentum)

Question 6

what is an impulse?

Answer 6

time in which a force (F) acts.

Question 7

what is the same as an impulse?

Answer 7

impulse = rate of change of momentum.

Question 8

if a ball rebounds of a wall in an elastic collision, what is the momentum of the ball after the collision?

Answer 8

-2mu

no change in speed so v=u

Question 9

in an elastic collision, if a ball bounces off a wall at angle cos(), what is the change in momentum of the ball?

Answer 9

-2muCos()

Question 10

state newtons third law.

Answer 10

when two objects interact they exert an equal and opposite force on each other.

Question 11

what happens to momentum in all collision?

Answer 11

momentum is ALWAYS conserved (if no external forces are acting).

Question 12

what is the difference between an elastic and inelastic collision?

Answer 12

KE is conserved in an elastic collision, not conserved in inelastic.

Question 13

energy cannot be ……………… or …………………….

Answer 13

created , destroyed

Question 14

what does the area under a force/distance graph equal?

Answer 14

work done.

Question 15

work done equation?

Answer 15

work done = force x distance moved in direction of force.

Question 16

if you turn through the angle do you use Cos() or Sine()

Answer 16

Cos()

Question 17

spring constant equation?

Answer 17

F = K x change in length.

Question 18

what does the are under a force/time graph show?

Answer 18

change in momentum.

Question 19

what does the area under a force/extension graph show?

Answer 19

work done to stretch a spring.

Question 20

work done to stretch a spring equation?

Answer 20

work done = 0.5 x force x change in length.

Question 21

when a lift is accelerating upwards, what is the tension in the cable?

Answer 21

T = mg + ma
(T = w + (F to accelerate))

Question 22

what are the three main forces involved with accelerating a lift?

Answer 22

weight, force to accelerate, tension in cable.

Question 23

does newtons first law apply to forces acting on the same object or different objects in contact?

Answer 23

different objects, same force.

Question 24

when a lift is accelerating downwards, what is the tension in the cable?

Answer 24

T = mg - ma ( negative acceleration)
(T = w + F to accelerate)

Question 25

pulley problem equation?

Answer 25

mg - mg = (M + m) x a.

accelerate at the same rate). (both equal result force

Question 26

how to calculate resultant force from x2 forces?

Answer 26

F2 - F1

Question 27

what is the gradient of a distance/time graph?

Answer 27

speed.

Question 28

what is the area under distance/time graph?

Answer 28

total distance travelled.

Question 29

what is the difference between distance and displacement?

Answer 29

displacement has a direction and magnitude.