Answer:
Normal Force is usually perpendicular to the movement and static friction usually means that there is no movement.
Explanation:
The work donde by any force on an object is equal to the displacement of the object multiplied by the component of the force that is in the direction of the displacement.
Normal force is usually perpendicular to the movement, so there is no component in the direction of the displacement. This is why it is zero in most circumstances.
<em>Static</em> friction on the other hand, usually means that there is no movement at all (it's static). It means that there is no displacement between the object and ground (in most cases). If there is no displacement, there is no work.
Answer:
840 cm
Explanation:
Note: A hydraulic press operate based on pascal's principle.
From pascal's principle
W₁/d₁ = W₂/d₂...................... Equation 1
Where W₁ and W₂ are the first and second weight, and d₁ and d₂ are the first and second diameter of the piston.
make d₁ the subject of the equation
d₁ = W₁×d₂/W₂................ Equation 2
Given: W₁ = 2100 kg, W₂ = 25 kg, d₂ = 10 cm = 0.1 m.
Substitute these values into equation 2
d₁ = 2100(0.1)/25
d₁ = 8.4 m
d₁ = 840 cm
Answer:
857.5 m
2.8583×10⁻⁶ seconds
Explanation:
Time taken by the sound of the thunder to reach the student = 2.5 s
Speed of sound in air is 343 m/s
Speed of light is 3×10⁸ m/s
Distance travelled by the sound = Time taken by the sound × Speed of sound in air
⇒Distance travelled by the sound = 2.5×343 = 857.5 m
⇒Distance travelled by the sound = 857.5 m
Time taken by light = Distance the light travelled / Speed of light
Time taken by light = 2.8583×10⁻⁶ seconds
First one is D and Second one is B
Answer: the wall contracts the force exerted by his head. The wall produces the opposite force which is equal to the force his head bangs the wall with.
Explanation: if his head exerts a much greater force than the wall can counteract the wall will be destroyed, if the wall exerts a much greater force than his head exerts he will be pushed far back and might even suffer a broken head.
The wall in this case provides the opposite reactive force.
