Answer:
F = 2520 N
Explanation:
We have,
The maximum acceleration of a fist in a karate punch is 4200 m/s². The mass of the fist is 0.6 kg.
It is required to find the force that the wood place on the fist. Force is given by the product of mass and its acceleration such that,
F = ma
So, the force of 2520 N is acting on the wood.
Answer:
Explanation:
s = s₀ + v₀t + ½at²
s = 0 + 0(15) + ½(6)(15²)
s = 675 m
Not sure what the free fall acceleration is needed for, but if the object is dropped from a high enough point, it will travel in 15 seconds
s = ½10(15²) = 2250 m if air resistance is ignored
b). The power depends on the RATE at which work is done.
Power = (Work or Energy) / (time)
So to calculate it, you have to know how much work is done AND how much time that takes.
In part (a), you calculated the amount of work it takes to lift the car from the ground to Point-A. But the question doesn't tell us anywhere how much time that takes. So there's NO WAY to calculate the power needed to do it.
The more power is used, the faster the car is lifted. The less power is used, the slower the car creeps up the first hill. If the people in the car have a lot of time to sit and wait, the car can be dragged from the ground up to Point-A with a very very very small power ... you could do it with a hamster on a treadmill. That would just take a long time, but it could be done if the power is small enough.
Without knowing the time, we can't calculate the power.
...
d). Kinetic energy = (1/2) · (mass) · (speed squared)
On the way up, the car stops when it reaches point-A.
On the way down, the car leaves point-A from "rest".
WHILE it's at point-A, it has <u><em>no speed</em></u>. So it has no (<em>zero</em>) kinetic energy.
