Answer:
F = 35651 [N]
Explanation:
To solve this problem we must use Newton's second law, which tells us that the sum of forces is equal to the product of mass by acceleration.
But first, we must use the following equation of kinematics to find acceleration.
where:
Vf = final velocity = 185 [m/s]
Vi = initial velocity = 0 (the cannon ball is at rest in the first moment)
a = acceleration [m/s²]
x = distance = 3.6 [m]
Now replacing these values into the equation:
(185)² = 0² + (2*a*3.6)
34225 = 7.2*a
a = 34225/7.2
a = 4753.5 [m/s²]
Now using Newton's second law we have:
F = m*a
where:
F = force [N]
m = mass = 7.5 [kg]
F = 7.5*4753.5
F = 35651 [N]
So the person weighs 65kg, and 9.4% of that is head, so 65*0.094 = 6.11 kg is the mass of the head. If we deaccelerate from 40 m/s to 0 m/s in 0.2 s, our total acceleration is: a = Δv/Δt = (0 - 40)/(0.2 - 0) = -200 m/s². We can then use Newton's second law, F = ma, to find the force, using m as mass of the head and a as our acceleration (we'll ignore the negative sign because we don't care about the force's direction here). F = ma = (6.11)(200) = 1222 N, a pretty large amount of force.
It now occurs to me that the easier way to do this, though slightly more advanced, is to use that Force is the derivative of momentum, or F = dp/dt, or with no calculus, F = Δp/Δt, where p is momentum and t is time. p = mv, where m is mass and v is velocity, so F = Δp/Δt = Δ(mv)/Δt = ((6.11)(0) - (6.11)(40))/(0.2 - 0) = (6.11)(40)/(0.2) = 1222 N. So yeah it's quicker, I feel this is less straight forward though.
Baking a cake would be a chemical change because the baking powder/soda undergoes through a reaction, you can tell because it generates bubbles/bumps when you bake it.
A chemical change is also irreversible so when you bake the cake, you cannot separate the ingredients.
So your answer would be B. Baking a cake
Hope this helps !
Answer:
dont know need points srry
Explanation:
A boiling pot of water (the water travels in a current throughout the pot), a hot air balloon (hot air rises, making the balloon rise) , and cup of a steaming, hot liquid (hot air rises, creating steam) are all situations where convection occurs.
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