A 12.0-g wad of sticky clay is hurled horizontally at a...

Name: Problem 25, Chapter 9: Physics for Scientists and Engineers with Modern Physics
Uploaded: 2021-01-07T09:36:38-08:00
Duration: 5 min 8 s
Channel: Vishal Gupta
Description: A 12.0-g wad of sticky clay is hurled horizontally at a 100-g wooden block initially at rest on a horizontal surface. The clay sticks to the block. After impact, the block slides 7.50 m before coming to rest. If the coefficient of friction between the block and the surface is 0.650, what was the speed of the clay immediately before impact?

A 12.0-g wad of sticky clay is hurled horizontally at a 100-g wooden block initially at rest on a horizontal surface. The clay sticks to the block. After impact, the block slides 7.50 m before coming to rest. If the coefficient of friction between the block and the surface is 0.650, what was the speed of the clay immediately before impact?

Key Concepts

Work-Energy Principle

The work-energy principle states that the work done by all forces acting on an object is equal to the change in its kinetic energy. This principle is applied here to relate the kinetic energy of the block-clay system immediately after the collision to the work done by friction as it slides to a stop.

Kinetic Friction

Kinetic friction is the resistive force acting between moving surfaces, which is proportional to the normal force and characterized by the coefficient of friction. Understanding kinetic friction is essential when calculating the deceleration and stopping distance of an object sliding along a surface.

Conservation of Momentum

In collisions where no external forces act in the horizontal direction, the total momentum before impact is equal to the total momentum after impact. This principle is crucial when analyzing events like a clay wad striking and sticking to a block because it allows us to relate the velocities of the objects before and after the collision.

Inelastic Collision

An inelastic collision is one in which the colliding objects stick together after impact, resulting in a loss of kinetic energy due to deformation, heat, or sound even though momentum is conserved. This concept is key when determining the combined velocity of the objects immediately after impact.

Transcript

00:01 Hi, the given problem on the horizontal rough surface.

00:05 Suppose this is the wooden block of mass capital m and here this is the clay of mass small m.

00:14 Suppose initial speed of the clay is u then the speed achieved by this wooden block after the impact with clay is v i and its final speed after traveling through 7 .5 meters means vf comes to be zero.

00:34 The weight of the combined block with clay will be acting vertically downward m plus m g so the reaction offered by this surface horizontal surface to this block will be n which is given by n is equal to m plus m into g and force of friction as the block will be moving rightward a force of friction will be acting on it towards left which is given as mu into n or we can say this is mu into m plus m into g then as per newton's second of motion this is also given as the product of mass of this block with the clay and the acceleration produced in this block along with the clay so canceling this m plus m acceleration in the motion of this block or we can say retardation as the block finally comes to rest.

01:34 This comes this will be given as negative of mu into g as this mu is given as 0 .650 then multiplied with 9 .8 meter per second is square.

01:50 Retardation in the motion of this block comes out to be minus v.

01:58 We will keep it as it is, we will calculate it later on.

02:01 Now this is the retardation in the motion of the block.

02:04 Now for the motion of the block, its initial speed is vi.

02:16 This speed is after the impact with the clay.

02:19 And that is missing, we don't know this...