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Answer:
Force the floor exerts on the passenger is 833 N.
Explanation:
- Weight of passenger (
) = mg = 85 × 9.8 N = 833 N
- Force the floor exerts on the passenger (
) = ?
- For the elevator with the speed as 2.0 m/s the net force is zero, it means that the force is balanced.
i.e. = -
= -mg = 833 N
hence is 833 N
- If the lift was not at a constant speed i.e. if it had acceleration (
) then the case would be different.
This type of a problem can be solved by considering energy transformations. Initially, the spring is compressed, thus having stored something called an elastic potential energy. This energy is proportional to the square of the spring displacement d from its normal (neutral position) and the spring constant k:
So, this spring is storing almost 12 Joules of potential energy. This energy is ready to be transformed into the kinetic energy when the masses are released. There are two 0.2kg masses that will be moving away from each other, their total kinetic energy after the release equaling the elastic energy prior to the release (no losses, since there is no friction to be reckoned with).
The kinetic energy of a mass m moving with a velocity v is given by:
And we know that the energies are conserved, so the two kinetic energies will equal the elastic potential one:
From this we can determine the speed of the mass:
The speed will be 7.74m/s in in one direction (+), and same magnitude in the opposite direction (-).