Energy, Grabity and Calculating Net Force of a Diver

[copitlory8]

Homework Statement

A 60.0-kg person, standing on a diving board, dives straight down into the water. Just before striking the water, her speed is 6.50 m/s. At a time of 1.75 s after entering the water, her speed is reduced to 1.10 m/s. What is the average net force (magnitude and direction) that acts on her when she is in the water?

Homework Equations

F=ma
Kinematics Equations
V=d/t

The Attempt at a Solution

I multiplied the mass times gravity (9.8) and get the downward force. I used 6.5 as the initial velocity and 1.1 as final velocity. Then deacceleration can be calculated. But i don't know where to go from here.

 

[kuruman]

You know the acceleration as she goes through the water and you know her mass. Can you find the net force acting on her from this information?

 

[kerimek]

I would approach this problem by first identifying all relevant variables and equations. In this case, we are given the mass (60.0 kg) and initial and final velocities (6.50 m/s and 1.10 m/s, respectively) of the diver, as well as the time (1.75 s) it takes for her to decelerate. We can use the equation F=ma to calculate the net force acting on the diver, where F is the net force, m is the mass, and a is the acceleration. In this case, the acceleration can be calculated using the kinematics equation V=d/t, where V is the average velocity and d is the distance traveled.

To determine the average velocity, we can use the average of the initial and final velocities (6.50 m/s and 1.10 m/s). This gives us an average velocity of 3.80 m/s. The distance traveled can be calculated using the equation V=d/t, where V is the average velocity and t is the time. In this case, the distance traveled is 6.65 m (3.80 m/s x 1.75 s).

Now, we can plug in all of these values into the equation F=ma. The mass of the diver is given as 60.0 kg, so we have F=(60.0 kg)(a). We can rearrange this equation to solve for the acceleration, which gives us a=F/m. Plugging in the values for force (which we are solving for) and mass, we get a= (F)/(60.0 kg). We now have all the necessary information to solve for the net force acting on the diver.

Substituting in the values for distance traveled (6.65 m) and acceleration (calculated as 2.17 m/s^2), we get F=(60.0 kg)(2.17 m/s^2)=130.2 N. This is the magnitude of the net force acting on the diver. The direction of the force would be downwards, as the diver is decelerating while moving towards the water.

In conclusion, the average net force acting on the diver when she is in the water is 130.2 N, directed downwards. This force is a result of the diver's deceleration as she enters the water.