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WorksheetsSci 8 Unit D 2.0 MA, SR, Efficiency, Energy
Total questions: 82
Worksheet time: 49mins
How many Joules of work is produced when 350N of force is used to move a car 5.21m?
Answer to nearest tenth.
(a)
The load has 5N of gravity. You pull on the forcemeter with 2.6N of force to lift up the load 10 cm. What is the Mechanical Advantage of the pulley system?
Answer to nearest tenth.
0.25
0.5
1.9
13
How does a single fixed pulley, like the one seen in the picture, help to lift a load?
changes the direction of the force
increases the amount of applied force
decreases the amount of applied force
allows you to pull the rope a shorter distance than the load moves
In which of these cases is work being done?
A student memorizes a poem.
A student pushes on a locked door.
A student carries a chair to the front of the classroom.
A student sits on the carpet
Using a lever, Josie is able to lift a 20,000 N vehicle off of the ground with a force of 921 N. What is the mechanical advantage of the lever?
Answer to the nearest tenth.
What is the mechanical advantage of this inclined plane?
Answer to the nearest tenth.
2
2.5
Which of the following is the most effective way to decrease the effort force needed to push a box to the top of the ramp in the picture?
cover the surface with carpet
increase the length of the ramp
increase the height of the ramp
decrease the length of the ramp
A 16 N force is applied to an object that moves 4.3m.
How much work was done?
3.7m
16J
68.8J
4.3 m
What is the efficiency of a machine if 55.3 J of work is done on the machine by the person, but only 14.3 J is produced by the machine on the load?
0.25 J
26%
386%
3.86 J
If the efficiency of a machine is 61.4%, then how much efficiency is lost to friction and heat?
1.4%
38.6%
61.4%
100%
A 100 N container is placed on a lever, and the force you apply to lift the container is 20 Newtons, what is the lever's mechanical advantage?
120 N
5 N
2000 N
80 N
What is the formula for mechanical advantage?
MA=
input force x output force
MA=
output force/input force
MA=
input force/output force
MA=
output force - input force
What is the mechanical advantage of a lever if you lift a load of 300 newtons and you only push down on the lever with 50 newtons?
250
50
60
6
True or False:
Most machines can be 100% efficient on Earth.
True
False
A machine's ability to convert input work to output work is called...
efficiency
power
input force
mechanical advantage
What is the speed ratio if you push down 10m on a lever and the load is lifted 2 m?
5
10
2
1
Machines don't reduce the amount of work energy you need to move objects, but they reduce ____________.
Weight
Mass
Input Force
Height
The unit of work is
Gram
True or False?
Work is done when you exert a force on an object and the object moves in the direction of the force.
true
false
If 68 Joules were necessary to move a 4 N crate, how far was the crate moved?
272 m
17 m
4.05 m
272 cm
A boy pushes on a parked car with a force of 200 N. The car does not move. How much work was done by the boy on the car?
200N
200J
0J
0N
Work is done because the person uses energy when applying the force
Work is done because the wall heats up at the place where the force is applied
No work is done
Density
Which is the rule that states: 'When force is applied to a confined fluid, the increase in pressure is transmitted equally throughout."?
Pascal's Law
Bernoulli's Principle
Archimedes' Principle
Newton's Law
What is the efficiency of the machine if the input work is 263 J and the output work is 142 J?
6.26%
54%
100%
260%
In what way do most machines transfer wasted energy to their surroundings?
by movement
by light
by electricity
by heat
If the handle on a wheel and axle is turned 1.6m to lift up a baby dragon 0.3m, what is the speed ratio of the pulley system?
0.3
0.48
1.6
5.3
12.3%
16.4%
30.2%
62.5%
If you push a wagon with a baby elephant up a 3.2m inclined plane using a force of 24N, and the 52 N baby elephant is lifted 1.1m, what is the efficiency of the inclined plane?
18%
46%
74%
96%
What is the efficiency of a typical fuel-combustion vehicle?
5%
25%
40%
60%
True or False: In an ideal situation with no friction, mechanical advantage is always less than the speed ratio when lifting a load.
true
false
Mechanical Advantage is also known as the ...
Hydraulic Output
Work Input
Speed Ratio
Force Ratio
A common form of input energy used 500 years ago to operate machines was...
oil
animals
gas
wind
True or False: Using a machine means that less work is done.
true
false
A mechanical engineer designs...
engines
amusement park rides
lawnmowers
all of the above
Which pulley system would have a higher mechanical advantage if both systems are lifting a 100N load up 20 cm off the ground?
A
B
A machine has an efficiency of 30%. How much energy is lost to friction or heat when the machine is operating?
70 %
There is not enough information given
50%
30%
In a combustion engine vehicle, most efficiency is lost due to
aerodynamics
tire pressure
friction in moving components
using the air conditioner
What is the mechanical advantage of pulley C
1
2
4
8
Which pulley system is the best to lift the load?
A
B
C
In order to reduce input effort force, the load should be placed on which piston?
A
B
Calculate the efficiency of the following device.
If you push down 2.8 m on a lever with 50 N and the 80N load goes up 1.3 m,
then what is the approximate efficiency of the lever?
14 %
30 %
73 %
93 %
Match the following to their SI measurements
Work
Joules (J)
Force
Newtons (N)
distance
meters (m)
time
seconds (s)
Identify whether work is done or not in the picture
Yes
No
doing homework
lifting a box
pushing on a wall
holding a box
It took 500 Newtons of force to push a car four meters. How much work was done?
2000 J
125 J
0.008 J
500 J
To lift the 200kg load, a person calculates the input force to be 120N. When the person tries to lift the load, the person must use more than 120N of input force.
The difference between the calculated input force and the actual input force is likely due to
gravity
friction
pressure
Pascal's Law
Look at the diagram of work input and work output for a fuel combustion car.
Which output work is considered wasted energy?
air conditioner
car moving forward
heat and friction
What is the primary energy source of this calculator?
battery
solar
gas
human
Which lever requires less effort force to lift a load?
longer lever
shorter lever
Example where friction is useful
when polishing a car
on a curling rink
to make a sled move faster
brakes on a bike
What is mechanical advantage?
The advantage a machine has over a bicycle
A measure of how much a simple machine reduces work
A measure of when is the best time to use a simple machine
the number of times a machine decreases the input force
What is the mechanical advantage for this lever?
1
2
1/2
8
Due to __________, the work put into a machine is always greater than the work output
energy
efficiency
friction
mass
The ratio of work output to work input is called
energy
efficiency
friction
mass
The primary source of energy for this vehicle is
solar
battery
gas
diesel
The primary source of energy for this calculator is
solar
battery
gas
diesel
The primary source of energy for this vehicle is
solar
electrical
gas
water
Which device has a battery as the primary source of energy?
To lift a load of sand, a worker calculates that 75N of force is required to lift the load. When lifting the load, the worker needed to apply more than 75N of force.
The most likely explanation for the difference between the calculated force and the actual force required is that (a) made it (b) to lift the load.
Pascal’s Law states that pressure applied to an enclosed fluid is transmitted
to the walls of the container which double the pressure.
equally in all directions throughout the fluid.
by the transfer force in the fluid.
to the opposite piston where it increases the force.
If a machine is only 30% efficient, it means that
30% of energy is destroyed
70% of energy is destroyed
30% of energy is converted into unusable energy
70% of energy is converted into unusable energy
If F1 is 57.2N and F2 is 161.5N, then what is the mechanical advantage of the hydraulic lift?
Answer to the nearest tenth.
(a)
Person A picks up a 30 N rock and raises it 2 m off the ground. Person B picks up a 25 N rock and raises it 3 m off the ground. Who put more work into moving a rock?
Person A
Person B
