Looking at decibel scale tables on internet, a "quiet whisper 1 meter away" is generally reported to have a sound intensity of about 20 dB, while a jackhammer 3 meters away produces a sound of about 100 dB of intensity, so option a) could be the correct one.
However, the other options could be considered correct as well, because without knowing the exact sound power produced by the whisper or by the jackhammer it's impossible to calculate the exact sound intensity with precision, and since the values reported in the three options are very similar, all the three of them can be considered as valid.
1). From the frame of reference of a passenger on the airplane looking out of his window, the tree appears to be moving, at roughly 300 miles per hour toward the left of the picture.
2). The SI unit best suited to measuring the height of a building is the meter.
3). 'Displacement' is the straight-line distance and direction from the start-point to the end-point, regardless of the path that was followed to get there.
The ball started out in the child's hand, and it ended up 2 meters away from her in the direction of the wall. So the displacement of the ball from the beginning to the end of the story is: 2 meters toward the wall.
Answer: - 7500N
Explanation:
Given the following :
Initial Velocity of car = 108km/hr
Time taken to stop after applying brakes = 4s
Mass of passengers in car = 1000kg
Force exerted by the brakes on the car =?
After 4s, then final Velocity (V) = 0
Initial Velocity (u) of the car = 108km/hr
108km/hr = (108 × 1000)m ÷ (3600)s = 30m/s
Force exerted = mass(m) × acceleration(a)
Acceleration of car = Change in Velocity with time
a = (v - u) / t
a = (0 - 30) / 4
a = - 30/ 4
a = - 7.5m/s^2
Therefore,
Force exerted = mass(m) × acceleration(a)
Force exerted = 1000kg × (-7.5)m/s^2
Force exerted = - 7500N
B. Strong nuclear
Because the strong nuclear force is the strongest at short distances, it dominates over the other forces and the two protons become bound, forming a helium nucleus (typically a neutron is also needed to keep the helium nucleus stable).