<span>When a person lifts the block, the block has more potential energy. Therefore the person does positive work on the block.
work = m g h
work = (4.5 kg) (9.80 m/s^2) (1.2 m)
work = 52.92 joules
The person's work on the block is 52.92 joules
When the block is being raised, the force of gravity opposes the motion. Therefore the force of gravity does negative work on the block.
work = - (force) (h)
work = - m g h
work = -(4.5 kg) (9.80 m/s^2) (1.2 m)
work = -52.92 joules
The work done by the force of gravity on the block is -52.92 joules
Note that when the block is moved horizontally, the potential energy does not change. Therefore there is no work done on the block when it moves horizontally (we are assuming that the kinetic energy does not change).</span>
Answer:
A vibration or oscillation is a periodically repeated reversal of the direction of movement.
Explanation:
Une vibration ou une oscillation est une inversion répétée périodiquement de la direction du mouvement.
Here is just another definition.
A vibration is periodic back-and-forth motion centerd around it's equilibrium.
Answer:
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Explanation:
In the first law, an object will not change its motion unless a force acts on it. In the second law, the force on an object is equal to its mass times its acceleration. In the third law, when two objects interact, they apply forces to each other of equal magnitude and opposite direction.
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Answer:
the density of gold is 19.3 g/cc
An energy of 25kJ is given out hence the reaction is exothermic.
<h3>What is a reaction?</h3>
Chemical reaction is said to occur when reactants combine leading to the formation of products. In a plot of the energy against the reaction profile, the topmost point of the graph is called the activation energy.
We know that a reaction is exothermic when reactants posses more energy than the products. Hence the enthalpy change for this reaction is;
ΔH = 5kJ - 30kJ = -25kJ thus the reaction is an exothermic reaction.
Now, the activation energy for the lighting of the match stick is high that is why a spark is required before the reaction gets underway. Heat is evolved in the process hence the reaction is exothermic. The energy of the reactants is greater than the energy of the products.
Learn more about exothermic reaction:brainly.com/question/10373907
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