Answer:
Approximately 
if that athlete jumped up at 
. (Assuming that 
.)
Explanation:
The momentum 
of an object is the product of its mass 
and its velocity 
. That is: 
.
Before the jump, the speed of the athlete and the earth would be zero (relative to each other.) That is: 
and 
. Therefore:
and 
.
Assume that there is no force from outside of the earth (and the athlete) acting on the two. Momentum should be conserved at the instant that the athlete jumped up from the earth.
Before the jump, the sum of the momentum of the athlete and the earth was zero. Because momentum is conserved, the sum of the momentum of the two objects after the jump should also be zero. That is:
.
Therefore:
.
.
Rewrite this equation to find an expression for 
, the speed of the earth after the jump:
.
The mass of the athlete needs to be calculated from the weight of this athlete. Assume that the gravitational field strength is 
.
.
Calculate using 
and 
values from the question:
.
The negative sign suggests that the earth would move downwards after the jump. The speed of the motion would be approximately .
Answer:
Option (C)
Explanation:
Einsteinium is an element of the periodic table grouped in the Actinide series, with atomic number 99. They are dense element and highly electro-positive. <u>They are highly radioactive</u>, i.e the atoms within the element are unstable and constantly decay until they reach a stable environment. It has 99 number of electrons and protons, 153 number of neutrons.
Due to its high radioactivity, they are health hazardous and can used in making nuclear weapons but their uses are very limited and unknown.
Thus, the correct answer is option (C).
- Angle (θ) = 60°
- Force (F) = 20 N
- Distance (s) = 200 m
- Therefore, work done
- = Fs Cos θ
- = (20 × 200 × Cos 60°) J
- = (20 × 200 × 1/2) J
- = (20 × 100) J
- = 2000 J
<u>Answer</u><u>:</u>
<u>2</u><u>0</u><u>0</u><u>0</u><u> </u><u>J</u>
Hope you could get an idea from here.
Doubt clarification - use comment section.
Answer:
Explanation:
Intensity of sound = sound energy emitted by source / 4 π d² , where d is distance of the source .
A )
Intensity of sound at 1 m distance = 60 /4 π d²
d = 1 m
Intensity of sound at 1 m distance = 60 /(4 π 1²)
= 4.78 W m⁻² s⁻¹
B )
Intensity of sound at 1.5 m distance = 60 /4 π d²
d = 1.5 m
Intensity of sound at 1 m distance = 60 /(4 π 1.5²)
= 2.12 W m⁻² s⁻¹
C )
Intensity of sound due to 4 speakers at 1.5 m distance = 4 x 60 /4 π d²
d = 1.5 m
= 4 x 60 /(4 π 1.5²)
= 8.48 W m⁻² s⁻¹
D )
Intensity of sound due to .06 W speaker must be 10⁻¹² W s ⁻² . Let the distance be d .
.06 /4 π d² = 10⁻¹²
d² = .06 /4 π 10⁻¹²
d = 6.9 x 10⁴ m .
Answer: D.) 3hrs
Explanation:
Given the following :
A boat can move at a constant velocity of 8 km/h; How long will it take for the boat to move 24 km
Recall:
Velocity = Displacement / time
For the boat to travel a distance of 24 km at a constant velocity of 8km /hr
Time taken = Displacement(distance moved) / velocity
Time taken = 24km / 8kmhr^-1
Tine taken = 3hrs
