Transcript P4 The Trolley experiment - School

P4 The Trolley experiment: information (a)
1. In P4, the knowledge that students need includes the ideas of:
a) force
b) momentum
c) speed
d) velocity (velocity is speed with a direction)
e) gravity strength
f) weight
g) potential energy
h) kinetic energy
i) work done by a force
2. The formulae that link the above quantities are:
a) Momentum = mass x velocity
b) Force x time = change in momentum
c) Weight = mass x gravity strength
d) Potential energy = mass x gravity x height lifted
e) Kinetic (movement) energy = ½ x mass x velocity squared
f) Work done = force x distance the force moves
g) Work done = change in energy
P4 The Trolley experiment: information (b)
Quantity
mass
force
momentum
speed
Velocity (speed with direction)
gravity strength
weight
potential energy
kinetic energy
work done by a force
Unit
P4 The Trolley experiment: information (b)
Quantity
mass
force
momentum
Unit
Kilogram (kg)
Newton (N)
Kg.m/s
speed
m/s
Velocity (speed with direction) m/s
gravity strength
weight
potential energy
kinetic energy
work done by a force
P4 The Trolley experiment: information (b)
Quantity
mass
force
momentum
Unit
Kilogram (kg)
Newton (N)
Kg.m/s
speed
m/s
Velocity (speed with direction) m/s
gravity strength
Newton per kg
weight
potential energy
kinetic energy
work done by a force
Newton
Joule (J)
Joule (J)
Newton metre (Nm) or Joule
P4 The Ticker tape timer (a)
Ticker tape timer
Ticker tape
trolley
string
pulley
Sloped ramp
masses
1. The ticker tape timer makes dots on the tape 50 times per second.
2. That means that it takes 1/10 th of a second to make 5 dots
3. What would the trolley be doing to make these dot patterns?
Start
a)
floor
P4 The Ticker tape timer (b)
Ticker tape timer
Ticker tape
trolley
string
pulley
Sloped ramp
masses
1. The ticker tape timer makes dots on the tape 50 times per second.
2. That means that it takes 1/10 th of a second to make 5 dots
3. What would the trolley be doing to make these dot patterns?
Start
a)
b)
floor
P4 The Ticker tape timer (c)
Ticker tape timer
Ticker tape
trolley
string
pulley
Sloped ramp
masses
1. The ticker tape timer makes dots on the tape 50 times per second.
2. That means that it takes 1/10 th of a second to make 5 dots
3. What would the trolley be doing to make these dot patterns?
Start
a)
b)
c)
floor
P4 The Trolley experiment (1)
Ticker tape timer
Ticker tape
trolley
string
pulley
Sloped ramp
masses
1. The ramp is sloped to allow (compensate) for _ _ _ _ _ _ _ _.
2. At the start, the trolley and the masses are not moving so they have
no _ _ _ _ _ _ _ _ .
3. The masses have been lifted up against the force of _ _ _ _ _ _ _ .
floor
P4 The Trolley experiment (2)
1. When the trolley is released, it accelerates along the ramp.
2. It has been pulled by the TENSION force in the string.
3. The moving trolley and masses are gaining _ _ _ _ _ _ _
energy.
4. The falling masses are losing gravitational _ _ _ _ _ _ _ _ _ energy.
5. The tension in the string pulls until the masses _________________ .
6. The ticker tape will have dots on it. They will be
a) the same distance apart ?
b) getting closer together ?
c) getting further apart
?
floor
P4 The Trolley experiment (3)
1. When they hit the floor, the falling masses have lost all their
gravitational _ _ _ _ _ _ _ _ _ energy.
2. The string goes slack so the trolley moves at a ____________
__________ until it reaches the end of the ramp.
3. When the string has gone slack, the dots on the tape will be
a) the same distance apart ?
b) getting closer together ?
c) getting further apart
?
P4 The Trolley experiment (4)
Analysing ticker tape.
1. Find the start of the tape. Mark it with an S (for START)
2. Find the first clear dot and draw a line through it across the tape.
3. Count another 5 dots and draw another line across the tape.
4. Continue for the whole length of the tape.
5. Measure the length of each tape section in cm.
6. Each 5-dot section takes 1/10th of a second to make: you can work out
the speed for each section by multiplying the section length by 10.
7. Fill in the results in a table. (next slide)
S
Section 1
section 2
section 3
P4 The Trolley experiment (5)
Analysing ticker tape.
1. Fill in a results table with these headings: extend to 10 sections.
Tape section
Journey time/s
1
0.1
2
0.2
3
0.3
4
0.4
Section length/cm
Section speed cm/s
2. Continue with a longer table till the end of the tape.
P4 The Trolley experiment (6)
Results:
Look at the table of results: find the highest speed reached by the trolley and masses.
Hghest speed that the moving objects reached ________ cm/s
Work out how long it took to reach that speed: Time taken = _______ s
P4 The Trolley experiment (7)
Calculations FOR EVERY RUN OF THE TROLLEY:
1. The total mass of the trolley and hanging masses is __________ g.
2. Convert to kilograms __________ kg
3. The highest speed that they reach is ___________ cm/s
4. Convert to m/s ___________ m/s
5. The momentum is mass x velocity (the same as speed in this experiment.)
6. Momentum = __________ x __________ = ___________ kg.m/s
The force which accelerates the moving objects is the WEIGHT of the
masses.
Mass x gravity strength = weight
8. The force pulls on the trolley for a short time.
9. Work out how long it took the trolley to reach its highest speed. ________ s.
P4 The Trolley experiment (8)
Calculations:
1. Write down these results:
FORCE PULLING THE TROLLEY AND MASSES
Momentum gained by the moving masses and trolley =________kg.m/s
RATE of momentum increase = momentum gained
time taken
2. You will have to draw a graph of Force against rate of momentum
change
3. Theory according to Newton suggests that the graph should be a
straight line because the two quantities are proportional.
If they are not, it means that some of the force is being used for other
things than pulling the trolley.
What else is the force doing?
P4 The Trolley experiment (9)
Calculations:
1. The masses have lost gravitational potential energy.
2. This is calculated by
GPE = mass (kg) x gravity strength x height lifted (m)
3. The moving trolley and masses have gained Kinetic energy.
This is calculated by
KE = ½ x total mass (masses + trolley) x speed squared
4. Do both calculations and compare your answers.
Gravity strength on the Earth = 10 N/kg
P4 The Trolley experiment (10)
Distance moved
floor
P4 The Trolley experiment (11)
floor
P4 The Trolley experiment (12)
Calculations:
1. The force from the weight of the masses does work on the moving
objects.
2. Weight = ______ N
Distance moved = _____ m
Distance
3. Work done = force x distance moved
moved
4.
= _______ x ________ = ________ Nm or J
5. The energy gained is kinetic energy
KE = ½ x mass x velocity squared
Work out the kinetic energy: ___________ J
Is the KE equal to the work done? If not, why not?
To trolley 10
floor
P4 The Trolley experiment (12)
Distance
moved
floor