momentum

Question 1

what is the relationship between final speed, initial speed, acceleration, and distance moved

Answer 1

v^2 = u^2 = 2as

Question 2

what is the relationship between mass, momentum, velocity?

Answer 2

momentum = mass x velocity

Question 3

what is the relationship between force, change in momentum, and time taken

Answer 3

force = change in momentum/time taken
F = (mv-mu)/t

Question 4

what is Newton’s second law?

Answer 4

force = mass x acceleration
( a force will cause the velocity of an object to change, therefore also its momentum. the greater the force, the faster the momentum changes AKA ‘the rate of change of momentum of an object is proportional to the resultant force on it’)

Question 5

what are the units for momentum?

Answer 5

kg m/s

Question 6

units for mass?

Answer 6

kg

Question 7

units for velocity?

Answer 7

m/s

Question 8

what is momentum?

Answer 8

a vector

Question 9

what is the letter used for momentum

Answer 9

p (lower case ‘p’ note P= pressure and a swirly p is density)

Question 10

what does the conservation of momentum say?

Answer 10

total momentum in a closed system stays the same
initial momentum=final momentum

Question 11

what happens to momentum in an explosion

Answer 11

before an explosion the momentum is 0 therefore the momentum after must also be zero as momentum is conserved.

Question 12

what is Newton’s 3rd law?

Answer 12

(change of momentum = impulse)
- the force of A on B is the same as B on A. Therefore, they both exert the same impulse on each other

Question 13

name some car safety features:

Answer 13

crumple zones (front and rear), seat belts being extendable, collapsable steering wheels, air bags, side impact bars

Question 14

how does an airbag help reduce injury?

Answer 14

the airbag increases the time it takes for your head to hit the wheel so the force decreases as change in momentum/time = force

Question 15

Using ideas of momentum and force, explain how a seat belt reduces the risk
of serious injury in a car crash

Answer 15

MP1. same momentum change (with or without a
seatbelt);
MP2. (but) time of impact increases;
MP3. (which) reduces rate of momentum change;
MP4. (therefore) reducing the (average) force;
MP5. the seat belt stretches (during collision);
MP6. acts;
(which) increases the area over which the force
MP7. (hence) pressure on body reduces;

Question 16

Suggest why a full-body harness is used in a racing car, instead of an
ordinary seatbelt.

Answer 16

A sensible suggestion;
e.g.
there is a higher momentum (transfer in collision)
there is a larger force during impact
straps have a greater area over which force acts
larger area of straps reduces the pressure

Question 17

The car has crashed into a
concrete wall.
State what happens to the momentum of the car during the crash

Answer 17

Momentum (of car and dummy) reduces to zero;
OR
All momentum is absorbed by the Earth;

Question 18

When the skater throws the snowball forwards, she slides backwards on the ice.
Explain why she moves in this direction.

Answer 18

MP1. mention of conservation of
momentum;
MP2. momentum of snowball and
skater;
MP3. (are) equal and opposite;
MP4. because momentum initially zero;