Physical Science B Semester Exam Answers
A gardener uses a wheelbarrow to move 20 kilograms of soil from a compost pile to a flower bed, a distance of 53 meters. The wheelbarrow has a mass of 17 kilograms. He expends 94.5 Newtons of force. How much work does the gardener do?(1 point)
Responses
1,961 N
1,961 N
3,496.5 N
3,496.5 N
5,008.5 N
5,008.5 N
135.4 N
To calculate the work done by the gardener, we need to use the formula:
Work = force x distance x cos(theta)
where theta is the angle between the force and the direction of motion. In this case, we can assume the angle is zero and cos(theta) is 1, since the force is being applied in the direction of motion.
The force given is 94.5 N. The distance moved is 53 meters.
To calculate the total mass moved, we add the mass of the soil and the wheelbarrow:
Total mass = 20 kg + 17 kg = 37 kg
Now, we can use the formula to calculate the work done:
Work = force x distance x cos(theta)
Work = 94.5 N x 53 m x 1
Work = 4,999.5 J
Therefore, the gardener does a work of 4,999.5 joules.
The closest answer option is 5,008.5 N, but this is not the correct unit for work, which should be joules (J).
A mechanic wants to use a compound pulley to lift a go-kart from the ground to work table, a distance of 1.2 meters. Without the pulley, 1,620 Newtons of force would be needed to lift the go-kart. If the pulley has a mechanical advantage of 4, how much force must the mechanic expend?(1 point)
The mechanical advantage of a compound pulley is determined by the number of supporting ropes that act on the load. Since the pulley has a mechanical advantage of 4, this means that the force needed to lift the load is one-fourth of the weight of the load.
If the weight of the go-kart is W, then its weight in Newtons is:
W = m * g
where m is the mass of the go-kart and g is the acceleration due to gravity (approx. 9.8 m/s^2).
To find the force needed to lift the go-kart using the pulley, we can use the formula:
Force needed = Weight of go-kart / Mechanical Advantage
Force needed = (m * g) / 4
If we solve this formula for m, we can substitute the value of m into the weight formula, and then substitute the result into the force formula to find the force needed.
Alternatively, we can simply divide the original force needed by the mechanical advantage to get the force needed with the pulley:
Force needed = 1,620 N / 4
Force needed = 405 N
Therefore, the mechanic needs to expend 405 Newtons of force to lift the go-kart using the pulley.
Which sentence best describes how a self-directed learner might investigate gravity?(1 point)
Responses
She would only follow her teacher’s instructions for testing the effects of gravity.
She would only follow her teacher’s instructions for testing the effects of gravity.
She would only join a team of students that is carrying out a gravity experiment.
She would only join a team of students that is carrying out a gravity experiment.
She would only repeat a gravity experiment that she researched online.
She would only repeat a gravity experiment that she researched online.
She would think of a way to test the effect of gravity, develop a plan, and carry out the investigation.
The sentence that best describes how a self-directed learner might investigate gravity is: "She would think of a way to test the effect of gravity, develop a plan, and carry out the investigation." This describes how a self-directed learner would take ownership of their learning and autonomously investigate how gravity works. They would use their initiative, creativity, and problem-solving skills to come up with a plan for testing the effects of gravity.
Which sentence best describes a self-directed learner?(1 point)
Responses
She always gets good grades.
She always gets good grades.
She rushes through a project very quickly.
She rushes through a project very quickly.
She makes sure to complete all class projects and homework.
She makes sure to complete all class projects and homework.
She uses her own initiative to set learning goals, find resources, and plan how to carry out investigations.
She uses her own initiative to set learning goals, find resources, and plan how to carry out investigations.
The sentence that best describes a self-directed learner is: "She uses her own initiative to set learning goals, find resources, and plan how to carry out investigations." This describes how a self-directed learner takes ownership of their learning and takes the initiative to plan and manage their own learning process. They are self-motivated, proactive, and responsible, and they actively seek out information and resources to achieve their learning goals.
Where do the forces that make atoms interact come from?(1 point)
Responses
from the electric fields of neutral molecules
from the electric fields of neutral molecules
from the electric fields of neutral subatomic particles
from the electric fields of neutral subatomic particles
from the electric fields of charged subatomic particles
from the electric fields of charged subatomic particles
from the electric fields of charged molecules