A 100g sample of hot copper is placed in a coffee cup calorimeter containing 100 grams of water at room temperature. After some
1 answer:
Answer:
Explanation:
When the hot copper and the liquid water reaches equilibrium, they have the same temperature; when this happens, the amount of heat released by the copper is equal to the amount of heat absorbed by the water:
where
is the mass of the copper
C_c=0.385 J/g˚C is the specific heat of copper
T_f=50˚C is the final temperature of both substances
is the mass of the water
C_w=4.184 J/g˚C is the specific heat of the water
T_c is the initial temperature of the copper
T_w=20˚C is the initial temperature of the water (room temperature)
Solving for T_c, we find:
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b) the net force on the car is zero.
Explanation:
Let's analyze each option one by one:
a) the force from the engine is greater than all the forces of friction. --> FALSE. In fact, the car is moving at constant velocity: this means that its acceleration is zero,
a = 0
and so Newton's second law becomes
where is the net force on the car and m is its mass. This means that the net force on the car is zero: so, the force from the engine cannot be greater than all the forces of friction, otherwise the net force cannot be zero.
b) the net force on the car is zero. --> TRUE, for what we said at point A)
c) the inertia is changing. --> FALSE. The inertia of an object just depend on the mass and the velocity of the object: as neither the mass nor the velocity are changing in this problem, then the inertia of the car is not changing.
d) the forces of friction are proportional to the acceleration of the car. --> FALSE. Generally, the force of friction acting on an object moving on a flat surface is
where is the coefficient of friction, m is the mass, and g the acceleration of gravity. Therefore, the force of friction does not depend on the acceleration of the car.
e) All of the above. --> FALSE
Learn more about net force and Newton's second law:
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