Answer:c
Explanation:work is force x distance. The wall doesn’t move any distance in A so that’s not work. B involves tasks that do work but I don’t think this is what they’re going for. For a short instance while kicking a ball, your foot is applying a force to the ball which moves a distance before following its own trajectory after contact with your foot. Because the contact has a short duration and isn’t instantaneous, this is work
Answer:
45.11 kmph and 12.530 m/s
Explanation:
Average speed = Total distance travelled / Total time taken
406/9 gives the answer in kilometers
And we convert it to m/s by multiplying it with 1000/3600
Answer:
The magnetic field is 
Explanation:
From the question we are told that
The mass of the metal is 
The current is 
The distance between the rail(length of the rod ) is 
The coefficient of kinetic friction is 
Generally the magnetic force is mathematically represented as
Given that the rod is moving at a constant velocity, it
=> 
Where 
is the kinetic frictional force which is mathematically represented as
So
=> 
substituting values
=> 
=>
Given:
h = 600 m, the height of descent
t = 5 min = 5*60 = 300 s, the time of descent.
Let a = the acceleration of descent., m/s².
Let u = initial velocity of descent, m/s.
Let t = time of descent, s.
The final velocity is v = 0 m/s because the helicopter comes to rest on the ground.
Note that u, v, and a are measured as positive upward.
Then
u + at = v
(u m/s) + (a m/s²)*(t s) = 0
u = - at
u = - 300a (1)
Also,
u*t + (1/2)at² = -h
(um/s)*(t s) + (1/2)(a m/s²)*(t s)² = 600
ut + (1/2)at² = 600 (2)
From (1), obtain
-300a +(1/2)(a)(90000) = -600
44700a = -600
a = - 1.3423 x 10⁻² m/s²
From (1), obtain
u = - 300*(-1.3423 x 10⁻²) = 4.03 m/s
Answer:
The acceleration is 0.0134 m/s² downward.
The initial velocity is 4.0 m/s upward.
