A 70kg man jumps 1.00 meters down onto a concrete walkway. His downward motion stops in 0.02 seconds. If he forgets to bend his knees, what force is transmitted to his leg bones?

a. 15 500N
b. 7 010N
c. 4 900N
d. 3 500N

How do you solve this

To solve this problem, we need to calculate the force transmitted to the man's leg bones when he lands on the concrete walkway.

The force can be calculated using Newton's second law of motion, which states that force (F) is equal to mass (m) multiplied by acceleration (a). In this case, the acceleration can be calculated using the equation:

a = change in velocity / time

Given that the downward motion stops in 0.02 seconds, the change in velocity can be calculated using the equation:

change in velocity = final velocity - initial velocity

Initially, the man's velocity is zero because he is at rest. The final velocity can be calculated using the equation:

final velocity = square root of (2 * acceleration due to gravity * height)

Given that the man jumps down 1.00 meter and the acceleration due to gravity is approximately 9.8 m/s^2, we can calculate the final velocity.

Now that we have the change in velocity and the time, we can calculate the acceleration. Finally, substituting the mass, acceleration, and solving for force, we can find the answer.

Let's calculate:

change in velocity = square root(2 * 9.8 m/s^2 * 1.00 m) = 4.43 m/s

a = change in velocity / time = 4.43 m/s / 0.02 s = 221.5 m/s^2

F = m * a = 70 kg * 221.5 m/s^2 = 15,505 N

Therefore, the force transmitted to the man's leg bones is approximately 15,505 N.

So, the correct answer is option a. 15,500N.

force*timestopping= mass*velocity change


v= sqrt(2*9.8*1)= sqrt(19.6)
force= 70*sqrt(19.6)/.02

Well, let's see if I can make this equation less bone-dry. First, we need to find the force transmitted to his leg bones. We can do this by using Newton's second law, which states that force equals mass multiplied by acceleration.

So, we know the mass of the man is 70kg and his downward motion stops in 0.02 seconds. To find the acceleration, we can use the formula:
acceleration = change in velocity / time

The change in velocity in this case is the distance the man jumps, which is 1.00 meter, divided by the time, which is 0.02 seconds. That gives us an acceleration of 50 m/s^2.

Now, we can calculate the force:
force = mass * acceleration

Plugging in the numbers, we get:
force = 70kg * 50m/s^2

If you crunch the numbers, you'll find that the force transmitted to his leg bones is 3,500N.

So, the answer is d. 3,500N. Remember, even if he forgets to bend his knees, this problem can still be solved with a little physics magic!

15 500 N

15 500N