Help with Retarding Force Homework Statement

• Ben_Walker1978
In summary, the conversation discusses a physics problem involving a pile-driver and a hammer. The problem is to determine the retarding force exerted by the ground on the combined mass of the pile and hammer, given the mass and height of the hammer, and the distance the pile is driven into the ground. The conversation also mentions the use of elastic collisions and conservation of momentum in solving the problem. The solution may involve assuming that the pile and hammer move together as the pile drives into the ground, and considering the effects of kinetic energy and energy conservation.
Ben_Walker1978

Homework Statement

I need help with the following question:

A pile-driver has a hammer mass of 1000 kg which is dropped onto a pile from a height of 5 meters. The pile is driven 0.5 meters into the ground. The pile has a mass of 500 kg. Calculate the retarding force exerted by the ground on the combined mass of the pile and hammer.

Thanks,

The Attempt at a Solution

So far i have this, this is for the hammer hitting the pile:

PE = Mgh

M = 1000Kg

g = 9.81 m/s

h = 5 meters

1000 x 9.81 x 5 = 49050 Joules

V^2 = 2gh

Square root of 2 x 9.81 x 5 = 9.9 m/s^1

Velocity = 9.9 m/s^1

But i am now stuck. How do i work out the pile going 0.5 meters into the ground. And the retarding force?

Have you learned about elastic and inelastic collisions? What do you know about the collision? What is conserved in the collision? Do the pile and the hammer move together as the pile drives into the ground?

Ben_Walker1978 and anorlunda
scottdave said:
Have you learned about elastic and inelastic collisions? What do you know about the collision? What is conserved in the collision? Do the pile and the hammer move together as the pile drives into the ground?

Hello,
I have not learned about the things you have mentioned. Yes i guess the pile and the hammer move in the ground together.

They may be closer to an Elastic Collision, which would have some "bounce". You may want to read up on this. https://en.wikipedia.org/wiki/Elastic_collision

If they move into the ground together, you can use Conservation of Momentum to determine the initial speed at which they move. Kinetic Energy will not be conserved (note that Energy is always conserved, but it may not all remain as Kinetic).

Whichever way you solve, put your assumptions in your solution. Draw a diagram to show what forces are acting on the objects.

1. What is retarding force?

Retarding force, also known as drag, is a force that opposes the motion of an object through a fluid (such as air or water). It is caused by the interaction between the object and the fluid it is moving through.

2. How is retarding force calculated?

Retarding force is calculated using the equation Fd = 1/2 * p * v^2 * Cd * A, where Fd is the drag force, p is the density of the fluid, v is the velocity of the object, Cd is the drag coefficient, and A is the cross-sectional area of the object.

3. What are some examples of retarding force in everyday life?

Some examples of retarding force in everyday life include air resistance when riding a bike, water resistance when swimming, and friction between a car's tires and the road.

4. How does retarding force affect an object's motion?

Retarding force acts in the opposite direction of an object's motion, slowing it down. This force can also cause an object to change direction or come to a stop.

5. How can retarding force be reduced?

Retarding force can be reduced by changing the shape of an object to make it more streamlined, reducing the object's speed, or by decreasing the density of the fluid it is moving through. Additionally, using lubricants can reduce friction and therefore reduce retarding force.

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