A student pushes a box across a rough horizontal floor. If the amount of work done by the student on the box is 100 J and the am
1 answer:
Answer:
60J
Explanation:
friction is the opposition to the motion of an object. Before a body can be set in motion, part of the energy or work-done must be used to overcome friction.
While kinetic energy is the energy associated with a body due to its motion.
Since friction tends to oppose the motion of a body,when a body start to move, some of the energy applied to the body to cause its motion is converted to heat due to friction.
Hence if a work-done of 100J is applied to a body that requires 40J of the work to overcome friction, the total change in the kinetic energy can be expressed as
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D. Free fall
Explanation:
An object is said to be in free fall when there is only one force acting on the body, which is the force of gravity.
Near the Earth's surface, the force of gravity acting on a body is given by
F = mg
where
m is the mass of the body
g is the acceleration of gravity (its value is )
The direction of this force is downward (towards the Earth's centre).
If we apply Newton's second law on an object in free-fall, we can find its acceleration. In fact, we have:
And substituting F,
So, every object in free-fall accelerates at towards the ground.
Learn more about free fall here:
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Answer:
k = 104.46 N/m
Explanation:
Here we can use energy conservation
so we will have
initial gravitational potential energy = final total spring potential energy
as we know that she falls a total distance of 31 m
while the unstretched length of the string is 12 m
so the extension in the string is given as
so we have