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

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

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

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

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

kepler used the data from tycho blahe (his mentor) to construct the laws of planetary motion.

jupiter is the largest planet in our solar system, having a mass and radius that are respectively, 318 and 11.2 times that of earth. suppose that an object falls from rest near the surface of each planet and that the acceleration due to gravity remains constant during the fall. each object falls the same distance before striking the ground. determine the ratio of the time of fall on jupiter to that on earth.