Science 7A

Force and Work Unit Test 7A

1. A person pushes a box. He applies a force of 400 newtons, and he pushes the box for a distance of 4 meters. After he stops pushing, the box slides forward another meter. How much work was done by the person?
(1 point)
a. 1,600 joules ***
b. 400 joules
c. 2,000 joules
b. 100 joules

2. In this pulley system, the pulleys will _____ the mechanical force required to lift the block and will change the _____.
(1 point)
a. decrease; direction of the force
b. increase; weight of the block
c. decrease; weight of the block
d. increase; direction of the force ***

3. Which list correctly orders effort (E), fulcrum (F), and load (L) for each lever class?
(1 point)
a. class 1 = F, E, L (or L, E, F)
class 2 = L, F, E (or E, F, L)
class 3 = F, L, E (or E, L, F)
b. class 1 = F, E, L (or L, E, F)
class 2 = F, L, E (or E, L, F)
class 3 = L, F, E (or E, F, L)
c. class 1 = L, F, E (or E, F, L)
class 2 = F, L, E (or E, L, F)
class 3 = F, E, L (or L, E, F) ***
d. class 1 = F, L, E (or E, L, F)
class 2 = F, E, L (or L, E, F)
class 3 = L, F, E (or E, F, L)

4. How do simple machines make work easier?
(1 point)
a. They increase the distance over which a force is needed, doing more work with less force. ***
b. They reduce the amount of force needed to move an object to do the same amount of work.
c. They decrease the distance needed between a person and an object, allowing the person to apply more force and do more work.
d. They magnify the force being applied, thereby decreasing the work they can do with no extra energy exerted by the person using the machine.

5. A person using a lever applies 98 Newtons to lift a 20-kilogram box. They apply the force over a distance of 4 meters to lift the box a distance of 2 meters. How much work is done?
(1 point)
a. 392 Joules ***
b. 40 Joules
c. 196 Joules
d. 80 Joules

6. A person is lifting a heavy box using a lever. What is the purpose of the lever in this situation?
(1 point)
a. to reduce the energy needed to lift the box while keeping the direction of the force the same
b. to reduce the force needed to lift the box and change the direction of the force
c. to reduce the force needed to lift the box while keeping the direction of the force the same
d. to reduce the energy needed to lift the box and change the direction of the force ***

7. Where is the fulcrum in this situation?
(1 point)
a. It is the point where the bar touches the smaller rock.
b. It is the point where the bar touches the boulder.
c. It is the point where the boulder touches the ground.
d. It is the point where the person’s hands push down on the bar. ***

8. In which situation did the car achieve the greatest efficiency? (Assume the cars all have the same mass.)
(1 point)
a. a car that traveled 70 kilometers on 5.0 liters of gas
b. a car that traveled 50 kilometers on 4.0 liters of gas ***
c. a car that traveled 90 kilometers on 6.0 liters of gas
d. a car that traveled 80 kilometers on 5.0 liters of gas

9. Which machine has the highest efficiency?
(1 point)
a. machine D
b. machine C ***
c. machine B
d. machine A

10. How does a pulley make work easier when it is used to lift an object?
(1 point)
a. It decreases the distance over which the force must be applied to lift the object.
b. It reduces the weight of the object being lifted.
c. It increases the amount of work produced to lift the object.
d. It changes the direction of the lifting force to work with gravity. ***

11. A certain lever system is only 30% efficient. What could make it more efficient?
(1 point)
a. Make a longer lever that will require less force. ***
b. Use a stiffer lever to reduce energy lost bending the lever.
c. Use it with a lighter load to make it easier.
d. Have more than one person help to lift the lever.

12. What is the efficiency of a ramp if 2,000 joules of energy results in 1,200 joules of work?
(1 point)
a. 24%
b. 60% ***
c. 32%
d. 80%

can someone please check my answers??

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  1. no

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  2. Noooooo I got a 50% on it

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  3. 1. 1,600 joules
    2. Decrease; direction of force
    3. Class 1= L,F,E
    Class 2= F,L,E
    Class 3= F,E,L
    4. They reduce the amount of force needed to move a object to do the same amount of work
    5. 392 joules
    6. To reduce the force needed to lift the box and change the direction of the force
    7. It is the point where the bar touches the smaller rock
    8. A car that traveled 80 kilometers in 5.0 liters of gas
    9. Machine c
    10. It changes the direction of the lifting force to work with gravity
    11. Use a stiffer lever to reduce energy lost bending the lever
    12. 60%

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  4. 100% thanks Bree

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  5. Bree is 100% correct :)))

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  6. Thank You @Bree

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  7. Thank you so much Bree

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    2. 👎

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