B. Explain why it is more difficult to move an object at rest, than to keep an object moving
1 answer:
Answer:
because the static friction is higher than the kinetic friction
Explanation:
Inertia is resistance to motion. Object resist changing its current motion or the rest position. This is the Newton's first law of motion
apart from this as the graph shows , the force needed to move when object at rest is higher than the force to change the motion of a moving body . this is because
<em>static friction > kinetic friction</em>
- static friction is the friction acts on a object resting on a rough surface
- kinetic friction is the friction acts on an object when it is moving on a rough surface
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Answer:
the power that must be supplied to the motor is 101.45 hp
Explanation:
Given that,
The weight of elevator = 1000lb
The motor exerts a constant force of 500 lb on the cable
The load has been hoisted s = 15 ft starting from rest
The motor has an efficiency of e = 0.65
According to the equation of motion:
F = ma
To calculate the output power:
P(out) = F. v
P(out) = 3 (500) * 21.98
P(out) = 32970 lb.ft/s
As efficiency is given and output power is known, we can calculate the input power.
ε = P(out) / P(in)
0.65 = 32970 / P(in )
P(in) = 50,723 lb.ft/s
P(in) = 50,723 / 500 hp
= 101.45 hp
the power that must be supplied to the motor is 101.45 hp