An elevator is being lowered at steadily decreasing speed by a steel cable attached to an electric motor. There is no air resist
ance, nor is there any friction between the elevator and the walls of the elevator shaft. Why does the upward force exerted on the elevator by the cable have a larger magnitude as the downward force of gravity on the elevator
In this case they indicate that the speed is less and less as it goes down, therefore the acceleration must be opposite to the speed, that is, the acceleration is upwards, consequently it is positive
We can see that since a> 0 the force F must have greater than the weight of the elevator
Please see below as the answer is self-explanatory.
Explanation:
At any time, there are two forces acting on the elevator: the tension in the cable T (upward) and the force of gravity (downward).
Taking the upward direction as positive, if we apply Newton's 2nd law, we will have the following equation:
Now, we know that the elevator is being lowered at a decreasing speed, which means that the acceleration must have an opposite direction to the displacement.
Since the displacement is downward, that means that the acceleration must be positive.
If a ≥ 0, this means that T- mg ≥ 0, so the tension T must have a larger magnitude as the downward force of gravity on the elevator.
The first part of the question the car is going in reverse or negative along the x axis. Then the second part the car is moving forward along the x axis. So the car would only have velocity in the current direction of movement. So our equation for velocity is as follows.
