Transcript 3_1 Energy and Work

3_1 Energy and Work
A
B
C
07 April 2016
Look at the forces
on these cars.
What can you say
about their
movement?
3_1 Energy and Work
A
B
C
07 April 2016
Accelerating
quickly left.
Accelerating
left.
Constant
velocity or
stopped.
07 April 2016
3_1 Energy and Work
• What do scientists mean by “work”?
• What is the connection between work and
energy?
• What happens to the work done by friction?
Work done
• Work done = energy transferred
• Work done (J) = force (N) x distance (m)
E.g.
A 20 Newton weight is lifted 1 metre above the ground.
How much work is done?
Work done = Force x distance
= 20 N x 1 m
= 20 Joules
Energy experiments
1. Biceps
a. Measure arm
length (m)
b. Lift weight.
c. Record number of
lifts in 1 minute.
3. Quadriceps
a. Weigh yourself in
Newtons.
b. Measure height of 1
stair.
c. Record number of
steps climbed in 1
minute.
Work done (J) = force (N) x distance (m)
2. Triceps
a. Lift weight above
your head.
b. Record number
of lifts in 1
minute.
4. Friction
1.
Pull the weight
along the bench
2. Pull the weight up
the slope
3. Record the force
needed each time.
Results
Experiment
Force
(N)
E.g. Weight
1 Biceps
2 Triceps
3 Quads
4 Friction
Total Distance
(m)
Arm Reps
Total
Energy
(J)
=Fxd
Conclusions
• Which exercise uses most energy?
• Where does the energy go?
• What does friction do to movement
energy?
• Do your measurements include all the
energy used? (Accuracy)
• How could you be more accurate?
Summary
• Work done = energy transferred
Workdone
done(J)
= energy
• •Work
= forcetransferred
(N) x distance (m)
Friction causes objects to
heat up when they are
rubbed together.
This can cause fires.
Experiment
E.g.
Force
(N)
Weight
Total Distance
(m)
Arm
Reps
Total
Energy
(J)
Experiment
E.g.
=Fxd
1 Biceps
1 Biceps
2 Triceps
2 Triceps
3 Quads
3 Quads
4 Friction
4 Friction
Experiment
E.g.
Force
(N)
Weight
Total Distance
(m)
Arm
Reps
Total
Energy
(J)
Experiment
E.g.
=Fxd
1 Biceps
1 Biceps
2 Triceps
2 Triceps
3 Quads
3 Quads
4 Friction
4 Friction
Force
(N)
Weight
Force
(N)
Weight
Total Distance
(m)
Arm
Reps
Total
Total Distance
(m)
Arm
Reps
Total
Energy
(J)
=Fxd
Energy
(J)
=Fxd