AS
work done =W = F.d = F d cosФ (Ф is angle between force F and displacement d) If a body/object is moving on a smooth surface (friction-less surface ) .There is no force acting on that body. F=0 so W=FdcosФ= (0)dcosФ ⇒ W=0
Now if a body is facing some amount of force but under the action of force there is no displacement covered. d=0 so W =FdcosФ= F(0)cosФ ⇒W=0
example: A person is applying a force on rigid wall but wall remains at rest there is no displacement occurs in wall.
The third term upon which work done dependent is angle between force and displacement i.e Ф. If Ф=90° then W= FdcosФ= Fdcos90⇒ W=0 ( as cos 90°=0)
Answer:
The fraction of the protons would have no electrons 
Explanation:
We are given that
Amoeba has total number of protons=
Net charge, Q=0.300pC
Electrons are fewer than protons=
We have to find the fraction of protons would have no electrons.
The fraction of the protons would have no electrons
=
The fraction of the protons would have no electrons
=

Hence, the fraction of the protons would have no electrons 
Infra-red has wavelengths just longer than visible light.
The new velocity after 4 s is 40 m/s
The height of the spaceship above the ground after 5 seconds is 1,127.5 m
The given parameters for the first question;
- initial velocity of the car, u = 76 m/s
- acceleration of the car, a = - 9 m/s²
The new velocity after 4 s is calculated as;
v = u + at
v = 76 + (-9)(4)
v = 76 - 36
v = 40 m/s
(5)
The given parameters;
- height above the ground, h = 500 m
- velocity of spaceship, u = 150 m/s
The height of the spaceship above the ground after 5 seconds is calculated as;

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Answer:
50.4÷1.18= 42.7m/s as speed is equal to the distance over the time taken