Physics forces

Question 1

Scalar quantities

Answer 1

Only have magnitude ,don’t have a direction
Mass
Energy
Temperature
Time
Speed
Distance

Question 2

Vector quantities

Answer 2

Have magnitude and have direction
Displacement-a distance in a specific direction
Acceleration
Force
Weight
Velocity
Momentum

Question 3

Forces
What is a force?
units
quantity

Answer 3

A pull or push that acts on an object due to the interaction with another object .
Vector quantity
Newton(N)

Question 4

What are the two types of forces?
What happens when two objects interact ?
What is an interaction pair?

Answer 4

Normal contact forces, Contact forces, and Non-contact forces .
There is a force produced on both objects when two objects react.
Pair of forces that act on each other that are opposite and equal.

Question 5

Noncontact forces
What are they examples ?

Answer 5

Objects that do not need to be touching for the force to act .
Gravitational force attracts all objects to other objects..
Magnetic force -between two poles in a magnet and on some materials placed in a magnetic field .attraction and repulsion.
Electrostatic force -Two charged objects .Attraction and repulsion

Question 6

What is a contact force?
eg

Answer 6

objects need to be touching for the force to act.(friction,air resistance,normal contact forces )

Question 7

what is gravity ?
What is mass ?
What is weight?why is it caused ?
what is gravitational field strength?

Answer 7

gravity-force of attraction between all objects
Mass -the amount of stuff in an object that remains the same everywhere (kg)
weight-Force acting on an object due to due to gravity caused by gravitational field around the earth.

gravitational field strength - It is the measure of the force of gravity in a particular location 9.8N(g)

Question 8

equation for weight
weight is ?meaning
Explain the relationship between between weight and mass ?
what do you use to measure weight ?

Answer 8

Weight(N)=Mass(kg)times Gravitational field strengh
Weight of an object is directly proportional to the mass of it balance(newtonmeter) t

Question 9

What is the center of mass?
where is this for uniform objects?

Answer 9

the point at which you assume the whole mass is concentrated.
for uniform objects (ones with the same density throughout and regular shape)this will be the center of an object

Question 10

What is a resultant force ?
How do you work out resultant force ?
What happens if the forces are balanced ?

Answer 10

A single force that can be used to replace a number of forces acting upon an object. Has the same effect as all the other forces acting together.
to work this out we subtract a smaller force from the bigger force
if forces are balanced resultant force will be 0.

Question 11

What happens if a resultant force moves an object?
What does the work ?

Answer 11

energy is transferred and work is done on the object .
Force does the work to move the object and energy is transferred from one store to another

Question 12

What happens when you push a carpet along a rough surface ?
EXAMPLE ANSWER

Answer 12

You are doing work against friction .Energy is being transferred to the kinetic energy store of an object because it starts moving but some is also being transferred to thermal energy store due to friction .
overall temp increase of object

Question 13

How to find out the work done
Vector diagrams

Answer 13

Work done(J)=Force(N)times distance
draw a parallelogram with a scale,draw line in middle vertically measure the length

Question 14

Elasticity
What happens if you apply a force on an object?
why must more than one force be applied ?
What is done ?
Elastic deformation

Answer 14

You may cause it to bend, stretch or compress .
Stretching forces are equal in magnitude but in opposite directions (balanced)
Elastic materials will always return to their original length or shape if we take away the forces acting on them .
Work is done when a force stretches or compresses an object and causes energy to be transferred to elastic potential energy of the store .

Question 15

What do you need to do in order to change the shape /length?
What is inelastic deformation?
Equation for elasticity?

Answer 15

in order to change an objects length or shape we have to apply more than one force .
if only applied one forces wouldn’t be balanced so object would simply move.
inelastic deformation -doesn’t return to original length when forces are removed (polymers)
Force(N) =spring constant (N,m)times Extension (m)]
Force (N)=spring constant (N,m)times by compression (m)
work done=elastic potential energy

Question 16

Required practical (6)Forces and elasticity
What does the bottom of the spring have?
Explain what you have to do ?
What does the graph tell us ?
How do we know the spring is elastic?

Answer 16

Attach meter rule and spring .
The top of spring must be at zero point on the meter rule .
Bottom of spring has a wooden split(as a pointer) which must be horizontal
1)Measure unstretched length first
2)Place a 1 N weight on spring (read new position)
3)Continue adding 1 N weights to the spring
4)Work out extension ,Plot the extension against the weight
The graph is a straight line going through origin (0)telling us extension is directly proportional to weight (LINEAR RELATIONSHIP between weight and extension)
spring is elastic as if we removed the weight it would return to 0 .

Question 17

What happens if you overstretch the spring ?
What does overstretching mean ?
How would we get spring constant ?

Answer 17

Non-linear graph -
If you overstretch the spring and then took force away it would still show an extension(inelastic deformation)
overstretching means we have exceeded the limit of proportionality
using Force(N,m)=spring constant times by extension
Weightdivide by extension .
Spring constant will be the same any part of the graph as long as we don’t exceed the limit of proprtionality

Question 18

Moments

Answer 18

Turning effect of a force
Moment Nm=Force(N)times by distance(m)
It’s a Newton-meter
When calculating a moment the distance has to be perpendicular from the pivot to the line of force

Question 20

What is a moment?
How is the size of the moment given ?
What does the force of a spanner do ?
In terms of the spanner, how could you increase the moment?
How would you get the maximum moment?
How would you get an object to not turn?

Answer 20

A turning effect of a force
Moment of force (Nm)=Force times by distance
Causes a turning effect
Longer distance spanner or a larger force.
Push at right angles to the spanner.
If the clockwise moment i s the same as the anti-clockwise moment