A crate is pushed up each of the two ramps shown in the diagram below. Based on the concept that simple machines make work easie
r, and assuming that both ramps are friction less, which statement is true?
Ramp B requires less force than ramp A.
Ramp A requires less force than ramp B.
Ramp B raises the crate higher than ramp A.
Ramp A raises the crate higher than ramp B.
Ramp B requires less force than ramp A.
Ramp A requires less force than ramp B.
Ramp B raises the crate higher than ramp A.
Ramp A raises the crate higher than ramp B.
1 answer:
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Answer:
A. when the mass has a speed of zero
Explanation:
In mass-spring system, the velocity and the acceleration are in anti-phase, which means that when one of the two quantities is maximum, the other one is zero, and vice-versa.
In fact:
- When the displacement of the spring is zero (x=0), the velocity is maximum, due to conservation of energy. In fact, as the displacement is zero, the elastic potential energy of the system (given by ) is zero, therefore the kinetic energy (given by
) must be maximum, and so the velocity (v) is also maximum. On the cotnrary, acceleration (a) is directly proportional to the restoring force of the spring, given by
so we see that when x=0, then the force is zero: F=0, and so the acceleration is zero as well.
- When the displacement of the spring is maximum, the velocity is zero, due to conservation of energy. In fact, as the displacement is maximum, the elastic potential energy of the system (given by ) is maximum, therefore the kinetic energy (given by
) must be zero, and so the velocity (v) is also zero. On the cotnrary, since acceleration (a) is directly proportional to the restoring force of the spring, given by
so we see that when x=maximum, then the force is maximum, and so the acceleration is maximum as well.
Based on this, the correct answer is
A. when the mass has a speed of zero
Answer:
a)
b)
c)
Explanation:
From the exercise we know the initial velocity of the projectile and its initial height
To find what time does it take to reach maximum height we need to find how high will it go
b) We can calculate its initial height using the following formula
Knowing that its velocity is zero at its maximum height
So, the projectile goes 1024 ft high
a) From the equation of height we calculate how long does it take to reach maximum point
Solving the quadratic equation
So, the projectile reach maximum point at t=2s
c) We can calculate the final velocity by using the following formula:
Since the projectile is going down the velocity at the instant it reaches the ground is: