# Find Velocity of the wooden block at t=4 sec

• Shivam
In summary: This method is the one to use because you are given the variable force as a function of time. If you were given the variable force as a function of position, then using the work-energy theorem would be more direct.
Shivam
Homework Statement
An initially stationary wooden block with a mass of 2kg is pulled horizontally along a time dependent force f(t)i. The coefficient of static and kinetic friction between the block and the table are 0.5 and 0.25 respectively. F(t) as a function of time is shown, then find

(i) if initial velocity of the block is zero, its velocity at 4 seconds will be ?
Relevant Equations
F=ma, f=(mu)N
Here's the given F-t graph

My Attempt...
Fsmax=10N & Fk= 5N
I made equatiom F=5t-5 ( by seeing Force force and Counteracting kinetic friction)
reduced the formula to a=(5t-t)/2 wrote a=dv/dt and solved it but got wrong answer.

Shivam said:
Problem Statement: An initially stationary wooden block with a mass of 2kg is pulled horizontally along a time dependent force f(t)i. The coefficient of static and kinetic friction between the block and the table are 0.5 and 0.25 respectively. F(t) as a function of time is shown, then find

(i) if initial velocity of the block is zero, its velocity at 4 seconds will be ?
Relevant Equations: F=ma, f=(mu)N

Here's the given F-t graph
View attachment 245621

My Attempt...
Fsmax=10N & Fk= 5N
I made equatiom F=5t-5 ( by seeing Force force and Counteracting kinetic friction)
reduced the formula to a=(5t-t)/2 wrote a=dv/dt and solved it but got wrong answer.
And since you have not shown your work, we'd just be guessing where you went wrong. The statement "wrote a=dv/dt" is NOT showing your work, it's just describing your work.

Shivam said:
Problem Statement: An initially stationary wooden block with a mass of 2kg is pulled horizontally along a time dependent force f(t)i. The coefficient of static and kinetic friction between the block and the table are 0.5 and 0.25 respectively. F(t) as a function of time is shown, then find

(i) if initial velocity of the block is zero, its velocity at 4 seconds will be ?
Relevant Equations: F=ma, f=(mu)N

Here's the given F-t graph
View attachment 245621

My Attempt...
Fsmax=10N & Fk= 5N
I made equatiom F=5t-5 ( by seeing Force force and Counteracting kinetic friction)
reduced the formula to a=(5t-t)/2 wrote a=dv/dt and solved it but got wrong answer.
The graph shows the applied force. Is the acceleration actually the graph shown divided by the mass? Does the block start to slide immediately after t = 0?

kuruman said:
The graph shows the applied force. Is the acceleration actually the graph shown divided by the mass? Does the block start to slide immediately after t = 0?
I know block starts to move at t=2 sec
Also at 2 sec kinetic friction(5N) starts to act and that's why I wrote -ve5 in force equation which is reduced by kinetic friction

So I take it you are not going to show your work.

phinds said:
So I take it you are not going to show your work.
Ok..sorry I'll show...just wait a minute.

phinds said:
So I take it you are not going to show your work.
I got the answer right this time ... It was calculation mistake, for all this time I thought my method was wrong... Sorry for causing trouble.
Is their is any other method can you tell me, The one you solved with

Last edited:
Shivam, you really need to learn to use the edit button. It's a bit ridiculous to make 3 or 4 posts in a row instead of just adding to the first one.

phinds said:
Shivam, you really need to learn to use the edit button. It's a bit ridiculous to make 3 or 4 posts in a row instead of just adding to the first one.
Ok..just tried the edit method... Do u have any other method to solve the problem with ?

Shivam said:
Ok..just tried the edit method... Do u have any other method to solve the problem with ?
This method is the one to use because you are given the variable force as a function of time. If you were given the variable force as a function of position, then using the work-energy theorem would be more direct.

Shivam

## 1. What does it mean to find the velocity of a wooden block at t=4 sec?

Finding the velocity of a wooden block at t=4 sec means determining the rate at which the block is moving at exactly 4 seconds after it has been set in motion.

## 2. Why is it important to calculate the velocity of the wooden block at t=4 sec?

Calculating the velocity at a specific time allows us to understand the motion of an object and make predictions about its future movement. In this case, it can help us determine if the block is accelerating, decelerating, or moving at a constant speed at 4 seconds.

## 3. How is the velocity of the wooden block at t=4 sec calculated?

The velocity at t=4 sec can be calculated by dividing the change in position of the block by the change in time. This is known as the average velocity formula: velocity = (change in position)/(change in time).

## 4. What factors can affect the velocity of the wooden block at t=4 sec?

The velocity of the wooden block at t=4 sec can be affected by several factors, including the initial speed of the block, the direction and magnitude of any external forces acting on the block, and the surface on which the block is moving.

## 5. How can the velocity of the wooden block at t=4 sec be measured?

The velocity of the wooden block at t=4 sec can be measured using a variety of methods, such as a stopwatch and measuring the distance the block travels in 4 seconds, or using motion sensors and software to track the block's movement and calculate its velocity at a specific time.

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