Answer:
kE=1/2mv^2
Explanation:
here
KE= 15000j
velocity =20m/s
mass=?
now
mass=
15000×2= (m)20^2
30000=m ×400
30000÷400=m
Mass (m)= 75
therefore mass is 75kilogram
Answer:
The amplitude of vibration of string will increase due to which loudness of sound will increase
Explanation:
As we know that the guitar is based on the principle of Resonance. When string of the guitar vibrates at a given frequency then the sound produced in the hollow part of the guitar will also be at same frequency.
This is known as resonance condition, so guitar will produce same frequency sound as that of frequency of string.
Now if the string is plucked with increasing level of force then it will increase the amplitude of vibrations of the string due to which the sound produced in the guitar will also be of same level.
So here we can say that amplitude and intensity of sound related as

so on increasing amplitude the intensity will increase and hence it will produce loud sound
Because rockets do accelerate in space and have been able to do so for a long time.
Answer: Option D
<u>Explanation:</u>
A rocket is made to reach the sky and its required destination by the burning of fuels in the rocket. So there is no need of any other external forces to propel them in space. As per Newton's third law, the action and reaction forces will help the rockets to escape the orbit of earth.
And then the remaining energy required by the rocket to travel in space will be obtained from the burning of fuels in the compartments. This burning of fuels in respective compartments will propel the rockets in space. So it is a complete myth that space travel was impossible before because of inability to provide propulsion in space.
Answer:
The car traveled the distance before stopping is 90 m.
Explanation:
Given that,
Mass of automobile = 2000 kg
speed = 30 m/s
Braking force = 10000 N
For, The acceleration is
Using newton's formula

Where, f = force
m= mass
a = acceleration
Put the value of F and m into the formula

Negative sing shows the braking force.
It shows the direction of force is opposite of the motion.


For the distance,
Using third equation of motion

Where, v= final velocity
u = initial velocity
a = acceleration
s = stopping distance of car
Put the value in the equation


Hence, The car traveled the distance before stopping is 90 m.