Answer:
The force has been reduced by 8018 N
Explanation:
The impulse exerted on the car during the crash is equal to the product of the force exerted and the duration of the collision, and it is also equal to the change in momentum of the car. So we can write:
where:
F is the force exerted on the car
is the duration of the collision
m = 1400 kg is the mass of the car
is the change in velocity of the car
We can re-write the equation as
In the 1st collision, the time is 1.5 seconds, so the force is
In the 2nd collision, the time is increased to 2.2 seconds, so the force is
Therefore, the force has been reduced by:
Answer:
B.) by interfering with sound waves
Explanation:
As we know that the interference of sound waves is of two types
1). constructive interference
2). destructive interference
now we know that constructive interference means the resultant intensity will be more than the intensity of interfering waves as here two waves are in same phase.
In destructive interference the resultant of two waves is given by the minimum resultant of the intensity as here the phase of two waves are opposite to each other.
So we will say that
here in case of noise cancelling headphones we know that the phase of noise is always made in opposite phase with the sound which is used to cancelled the noise.
This will reduce the noise and we will get a clear sound
Answer:
P = 14700 J
Explanation:
Given that,
Mass of a piano, m = 75 kg
It is delivered throughout the window of a 6th story apartment which is 20 m above the ground.
We need to find the potential energy of the piano. It is given by :
P = mgh
Putting all the values,
P = 75 kg × 9.8 m/s² × 20 m
P = 14700 J
So, the potential energy of the piano is 14700 J.
Answer:
The work done in pulling the bucket to the top of the well is 3,360 ft-lb
Explanation:
Given
Weight = 6 lb
Depth = 80ft
Weight of Water = 40lb
Rate = 2ft/s
Leak Rate = 0.2ft/s
Calculating Workdone to lift the bucket
Work = Force * Distance
Work = 6 * 80
Work = 480ft-lb
At time t, the bucket is xi = 2t above the original depth of 80ft.
t = ½xi
But it now holds 40lb - 0.2t lb of water
= 40 - 0.2(½xi)
= 40 - 0.1xi.
This is the size of the water when it is x ft above the original depth.
To move this amount of water, we need (40 - 0.1xi)∆x
So, W = ∫(40 - 0.1xi)∆x {1,n}
Where n = 80
W = ∫(40 - 0.1x)dx {0,80}
W = 40x - ½(0.1x²) {0,80}
W = 40x - x²/20 {0,80}
W = 40(80) - 80²/20
W = 3200 - 320
W = 2880 ft-lb
The work done in pulling the bucket to the top of the well = 2880 + 480
= 3,360 ft-lb
