22 March 2016
2.3 Force and acceleration
Resultant forces
Find the resultant force on these objects.
10N
5N
10N
20N
15N
10N
30N
10N
10N
22 March 2016
2.3 Force and acceleration
5N
30N
20N
5N
2.3 Force and acceleration
22 March 2016
LO’s
Be able to explain how force and mass affect
acceleration
The F18 Hornet aircraft
takes off at 140mph and
weighs almost 30 tons.
Aircraft carriers are not
long enough for it to reach
this speed. Steam catapults
help the launch.
© V Majer
How are force and acceleration connected?
Diagram
Trolley
String
pulley
Ramp
Method
1.
2.
3.
4.
5.
Set up apparatus as shown.
Attach a 50g mass to the
end of the string.
Time how long it takes for
the trolley to travel 1
metre.
Add another 50g and
repeat.
Take 5 different readings.
Results
Weight (N) Time (s)
Weight
Acceleration is proportional to force
• The mass pulls the trolley along the
track, and it accelerates because of
_______.
• If we increase the weight (a force),
acceleration will ______.
Force
Complete this
sketch graph.
Acceleration
Acceleration is proportional to force
• The mass pulls the trolley along the
track, and it accelerates because of
gravity.
• If we increase the weight (a force),
acceleration will increase.
Force
Force increases so
the acceleration
increases.
Acceleration
Acceleration is inversely proportional to mass.
• If this time we change the mass of the
object being pulled, increasing it by 1kg.
• The following graph is obtained.
acceleration
mass
Check
You should be able to:
All
Be able to explain that if force is increased
acceleration is increased and if Mass is increased then
acceleration is decreased.
Most
Be able to use equation ( if given)
Force = mass x acceleration.
Practical.
• A trolley rolls along a track.
• A ticker timer is used to calculate
speed and acceleration
• Different forces are use to start it
moving
• Then different masses are added and
the experiment is repeated
Results
1N 2N 3N
1st reading (taken at
0s)
2nd reading (taken at
1s)
Change in speed (m/s)
0m
0m
0m
1m
2m
3m
Acceleration (m/s²)
Copy and complete
Question
• What is the relationship between
the acceleration and the force?(use
an ER...ER relationship)
Results
1kg 2kg 3kg
1st reading (taken at 0s)
0m
0m
0m
2nd reading (taken at
1s)
Change in speed (m/s)
1m
0.5m
0.33m
Acceleration (m/s²)
Copy and complete
Question
• What is the relationship between
the acceleration and the mass? (
Use an ER............ER relationship)
We have discovered:
1. As force increases so does
acceleration. (This is common sense,
the harder you push something, the
faster it moves!)
2. As weight increases, acceleration
decreases. (Again, this isn’t rocket
science! If something’s heavy it’s hard
to shift!)
Copy
Mathematical relationships
Force
=
newtons
Mass
kilograms
X
Acceleration
metres/second²
F
MX
A
Copy