Physics 3.2

Question 1

What is the equation for Newtons second law?

Answer 1

Force= mass * acceleration

Question 2

What is weight?

Answer 2

-The force which causes an object to accelerate towards the earths core, this is due to the pull of gravity
-Weight=mass in kg * acceleration of free fall in ms^-2

Question 2

What is tension?

Answer 2

-Tension is the force experienced by a rope, wire, string or cable that is being supported, hung, pulled and rotated
-Tension can cause objects to change shape or accelerate

Question 3

What is the normal contact force?

Answer 3

-Known as the reaction force and acts perpendicular to the point of contact.

Question 4

What is Upthrust?

Answer 4

-The upwards force that a liquid or gas will exert on a body in it, for a liquid this is due to the displaced water.

Question 4

What is friction?

Answer 4

-Occurs between every two objects in contact and is caused by interatomic and intermolecular forces
-Friction opposes the motion but don’t depend on velocity

Question 5

What is terminal velocity?

Answer 5

-When the drag becomes equal to the weight of a falling object so the object falls at a constant velocity as there is no resultant force.

Question 6

When is an object in equilibrium?

Answer 6

-When an object has zero resultant forces;.

Question 7

Do revision Cards

Question 8

How is a turning moment created and what is the equation for it?

Answer 8

-When a force is applied to an object often perpendicular to the objects axis it causes it to rotate creating a turning moment.
-Turning moment= magnitude of force * perpendicular force from the pivot

Question 9

What is the principle of moments?

Answer 9

-For an object to be in rotational equilibrium, the sum of the clockwise moment must be equal to the sum of the anticlockwise moment

Question 10

What is a couple and a torque

Answer 10

-Couple: when two equal antiparallel forces act to produce a rotation
-Torque: The turning effect of a couple

Question 11

What is the centre of mass?

Answer 11

-Where the whole mass of an object can be thought of as acting, for symmetrical objects finding the centre of mass is easy if the mass is evenly distributed
-The centre of mass can also be located at a point where there is no matter present e.g a horseshoe, this is because the mass is evenly distributed in that spot.

Question 12

What happens when a force acts through the centre of mass and doesn’t?

Answer 12

-When a force acts directly through the centre of mass the object will either accelerate or move at constant speed in a straight line
-If the force doesn’t act through the centre of mass the object will move with a rotational motion this is because a turning effect has been set up a distance from the centre of mass

Question 13

What is the centre of gravity?

Answer 13

-Single point where all the weight of an object can be thought to act through

Question 14

Describe an experiment to find the centre of mass/gravity of an object

Answer 14

1. Make three random holes in the object
   2.Hang the shape by the first hole and let it come to rest ( a suspended body will always come to rest with its centre of mass directly below it)
2. Draw a line vertically downwards and repeat for the other two holes
   4.Where the lines cross is the centre of mass

Question 15

How is stability and centre of mass related?

Answer 15

-Objects that have a low centre of mass and wide base area tend to be more stable than those with high centre of mass and small base area
-Objects tend to topple when the centre of mass lies outside the width of the base

Question 16

What is the equation for density?

Answer 16

p=m/v

Question 17

How do you calculate the density of regular 3D shapes?

Answer 17

-Work out volume using a ruler and the equation for volume
-Use a mass balance to determine its mass
-Put into the equation p=m/v

Question 18

What is Archimedes principle?

Answer 18

-The upthrust exerted on an object suspended in water is equal to the weight of fluid displaced
-Therefore an object more dense than the liquid its suspended in will sink and less dense will float

Question 19

What is pressure? its equation and its units?

Answer 19

-Pressure is the force per unit area and is vector quantity as it has both direction and magnitude
-Pressure=force/area
-The units for pressure are either newtons per square metre or pascals

Question 20

When is pressure at its highest?

Answer 20

-Small surface area where the force is exerted
-Large force exerted

Question 21

Why does pressure increase with depth?

Answer 21

-More force is exerted by the weight of the fluid above when you go deeper