mechanics-newtons laws, terminal velocity,momentum

Question 1

What is newtons first law ?

Answer 1

If no resultant force acts upon a system it will remain at a constant velocity or remain at rest.

Question 2

What is newtons second law ?

Answer 2

The rate of change of momentum(acceleration) is directly proportional to the force acting upon it .

Question 3

Newtons second law is represented by the equation …

Answer 3

F=MA

Question 4

What is newtons third law ?

Answer 4

When two objects interact they exert equal and opposite forces upon each other.

Question 5

What is tension ?

Answer 5

A pulling force applied by a cable/rope.

Question 6

Why does tension act away from the contact point ?

Answer 6

Because it is a pulling force.

Question 7

What factors affect air resistance ?

Answer 7

Cross sectional area
shape of object
fluid density
velocity of object

Question 8

What is terminal velocity ?

Answer 8

When drag force is equal to driving force.

Question 9

Describe and explain motion of a skydiver before parachute is opened.

Answer 9

As soon as they leave the plane no air resistance because no vertical velocity.
Then they accelerate due to gravity until acceleration reaches 0 when drag=gravity.

Question 10

Describe and explain motion of a skydiver after parachute is opened.

Answer 10

When parachute opens cross sectional area increases therefore air resistance increases therefore acceleration decreases
Velocity downwards increases due to acceleration by gravity until air resistance is equal to gravity where there is 0 acceleration.

Question 11

What is momentum ?

Answer 11

MV=P

Question 12

What are the 2 units for momentum ?

Answer 12

kgms-1
Ns

Question 13

Is momentum scalar or vector ?

Answer 13

Vector.

Question 14

What is the total momentum of a 2 identical balls with the mass of 2kg with one moving right at velocity of 4ms-1 and the other left 2ms-1

Answer 14

4kgms-1 right.

Question 15

How can rate of change of momentum be calculated ?

Answer 15

dp/dt=F

Question 16

How do you calculate momentum of a fluid flowing ?

Answer 16

Calculate volume of fluid produced per second
Calculate mass per second using D=M/V
length of prism of fluid per second is equal to velocity
Use P=MV to calculate momentum

Question 17

What is the density of water ?

Answer 17

1000kgm-3

Question 18

What is impulse equal to ?

Answer 18

change in momentum
force/dt

Question 19

What is the area under a force time graph equal to ?

Answer 19

Impulse.

Question 20

Explain how crumple zones in cars work ?

Answer 20

Crumple zones are parts of the car which deform during a car crash to increase time in contact with the body it collides with because Force exerted = change in momentum / time. therefore if time increases force decreases.

Question 21

What is conservation of momentum ?

Answer 21

For a system of interacting objects the total momentum remains constant as long as no external force acts.

Question 22

What is a elastic collision ?

Answer 22

A collision where there is no loss in kinetic energy.

Question 23

What is a explosion ?

Answer 23

Where two objects which are initially at rest fly apart with equal and opposite momentum.

Question 24

A cannon with the mass 500kg fired a cannonball with the mass of 20kg at the speed of 24ms-1. What is the speed of the recoil ?

Answer 24

-0.96ms

20x24=480
0=480-500x?
?=0.96
Negative due to it going in the opposite direction of the cannonball