Force

Question 1

What is Newton’s 1st Law?

Answer 1

-The velocity of an object will not change unless a resultant force acts on it
-It will either be travelling at a constant speed or is stationary, if it has no resultant force
-It will accelerate in the direction of the resultant force
-F=ma if F = 0, then a = 0

Question 2

What is Newton’s 2nd Law?

Answer 2

-F=ma
-More force = More Acceleration
-More mass = Less Acceleration

Question 3

What is Galileo’s theory?

Answer 3

-All objects fall at the same rate if you ignore air resistance

Question 4

What is Newton’s 3rd Law?

Answer 4

-If object A exerts a force on object B, then object B exerts an equal but opposite force back on A
-Applies in all situations and to all types of force, however they have to be the same type

Question 5

What is fluid friction or drag?

Answer 5

-The force depends on the viscosity of the fluid
-It increases as speed increases
-The larger the area of the object, the greater its resistance
-A projectile is slowed by air resistance

Question 6

What is friction?

Answer 6

-A force which opposes motion
-Always acts in the opposite direction to the motion of the object
-They can never speed things up or start moving something
-Convert kinetic energy into heat and sound

Question 7

What is terminal velocity?

Answer 7

-When the driving force stays the same all the time, and the frictional force is equal
-The acceleration and resultant force is 0

Question 8

What is the conservation of momentum?

Answer 8

-Assuming no external forces act
-Total momentum before equals total momentum after
-Forward momentum equals backwards momentum

Question 9

How does Newton’s Second Law explain momentum?

Answer 9

-The rate of change of momentum of an object is directly proportional to the resultant force which acts upon it

Question 10

How does Newton’s Third Law explain momentum?

Answer 10

-If object A collides with object B and exerts a force on B for a time, newton’s third law says that the object B will also exert a -force on A for the same time
-If you add the two it will equal 0 which shows its conserved

Question 11

What is work done?

Answer 11

-The amount of energy transferred from one form to another when a force causes a movement
-Is the increase in potential energy not it total potential energy

Question 12

What are 4 examples of Work done?

Answer 12

-Lifting a box: Work is done against gravity, and is converted to gpe
-Pushing a chair across a floor: Work done against friction, and is converted to heat
-Pushing two magnetic north poles together: Work done against the magnetic force, and is converted to magnetic energy
-Stretching a spring: Work done against the stiffness of the spring, and is converted to elastic potential energy

Question 13

What is a joule?

Answer 13

-One joule is the work done when a force of 1N moves an object through a distance of 1m

Question 14

What is power?

Answer 14

-The rate of doing work, or the amount of energy transferred per second
-The watt is equal to Js^-1

Question 15

What is a body’s mass?

Answer 15

-The mass of an object is the amount of matter in it
-The greater the object’s mass, the greater its resistance to a change in velocity

Question 16

What is weight?

Answer 16

-The force experienced by a mass due to its gravitational field

Question 17

What is the centre of gravity of an object?

Answer 17

-Is the single point that you can consider its whole weight to act through
-The object will always balance around this point

Question 18

How can you find an objects centre of mass?

Answer 18

-A regular object is by symmetry
-An irregular object is by hanging it from a point and drawing a vertical line from it, using a plumb bob and then doing that in multiple point, the centre of gravity is the point in which the lines cross

Question 19

How does the centre of gravity affect stability?

Answer 19

-An object will be stable with a low centre of gravity and a wide base
-An object will topple if a vertical line, line of action, downwards from the centre of gravity falls outside its base area, as its causing a moment/turning force around a pivot

Question 20

What is a moment?

Answer 20

-The turning effect of a force and depends on its size and how far the force is applied from the turning point/axis of rotation
-The principle of moments states that for an object to be balanced, the sum of the clockwise moments will be equal to its anticlockwise moments

Question 21

How does our body act as a lever?

Answer 21

-An effort force, muscles, acts against the load force, the weight of the arm, by means of a rigid object, the bone, rotating around a pivot, the joint

Question 22

Why do things fall over?

Answer 22

-If the centre of gravity is to one side of a pivot then it will turn as there is no opposite force
-If the centre of gravity is on the pivot, then it won’t turn