A running back holds 0.25 kg football and runs 100m down the football field. In addition to scoring six points for his team, he also does __

Question

A running back holds 0.25 kg football and runs 100m down the football field. In addition to scoring six points for his team, he also does ___ work on the football

A) no
B) 25 J of
C) 100 J of
D) 250 J of

Select the option which will cause a worker to do the maximum amount of work.
A) Using a lever to lift 100 newtons up to 4 meters on to a shelf
B) Using her hands to lift 200 newtons up 1 meter on to a table
C)Using a ramp to lift a 200 newton box up 1 meter into a truck
D) Using a pulley to lift to 100 newton box up 3 meters onto a platform

The power resulting from 420 Nm of work being completes in 3 seconds
A) 140 Joules
B)140 Newton-meters

What do you know about the law of conservation of energy? Check all the statements that are true

A)The total amount of mass in a system remains constant regardless of the changes that take place in system
B) Energy is neither creates or destroyed, it only changes form
C) Half-way down the ramp, PE = 50J and KE = 50J
D) In a closed system, a system that isolated from its surrounds, the total energy of the system is conserved

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Thu Hương 3 weeks 2021-08-23T23:32:07+00:00 1 Answers 0 views 0

Answers ( )

    0
    2021-08-23T23:34:06+00:00

    Answer:

    1) there is no work done on the system

    2) A) Using a lever to lift 100 newtons up to 4 meters on to a shelf

    3) P = 140 W

    4) D) In a closed system, a system that isolated from its surrounds, the total energy of the system is conserved

    Explanation:

    1) As we know that work done is the product of force and the displacement of the point of action where force is applied

    So here we have

    W = 0

    as there is no displacement in the direction where the force is applied

    2)As we know that work is product of force and displacement

    So we will have

    W_1 = 100 \times 4 = 400 J

    W_2 = 200 \times 1 = 200 J

    W_1 = 200 \times 1 = 200 J

    W_1 = 100 \times 3 = 300 J

    So maximum work is done on

    A) Using a lever to lift 100 newtons up to 4 meters on to a shelf

    3)

    As we know that power is rate of work done

    so we have

    P = \frac{W}{t}

    P = \frac{420}{3}

    P = 140 W

    4)

    As per energy conservation we know that

    D) In a closed system, a system that isolated from its surrounds, the total energy of the system is conserved

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