How Do You Calculate Braking Force Without Kinetic Energy?

  • Thread starter Thread starter rokr32
  • Start date Start date
  • Tags Tags
    Car
AI Thread Summary
To calculate the average braking force without using kinetic energy, the problem states that a car comes to rest in 15 meters, with an average resistive force of 2400N. The initial approach involved setting up an equation based on forces, but there was confusion regarding the use of the term "15F." The discussion emphasizes the importance of considering the direction of forces, as signs indicate their orientation in a coordinate system. Ultimately, the correct average braking force is confirmed to be 2.6 x 10^3N. A suggestion is made to draw a free body diagram to visualize the forces acting on the car.
rokr32
Messages
5
Reaction score
0

Homework Statement


1o27w6.jpg


The driver applies the brakes and the car comes to rest in 15m. Calculate the average braking force exerted on the car in coming to rest.

The average resistive force acting on the car is 2.4 x 103N

Homework Equations


F=ma
SUVAT maybe?

The Attempt at a Solution


When using KE = 1/2mv2, the problem is easy to solve. However, I'm not allowed to use this. Therefore, I have NO IDEA how to solve this.

One approach I took is, given that the average resistive force is 2400N, I did:
15F + 2400 = 0
F = -160N.

Then, given that the signs are irrelevant, I can add 160N to 2400N and get 2560N which rounds to 2.6 x 103N.

By the way, the answer should be 2.6 x 103N

Thanks :D
 
Physics news on Phys.org
rokr32 said:

Homework Statement


1o27w6.jpg


The driver applies the brakes and the car comes to rest in 15m. Calculate the average braking force exerted on the car in coming to rest.

The average resistive force acting on the car is 2.4 x 103N

Homework Equations


F=ma
SUVAT maybe?

The Attempt at a Solution


When using KE = 1/2mv2, the problem is easy to solve. However, I'm not allowed to use this. Therefore, I have NO IDEA how to solve this.

One approach I took is, given that the average resistive force is 2400N, I did:
15F + 2400 = 0
F = -160N.
Um, where does the 15F come from?
Then, given that the signs are irrelevant, I can add 160N to 2400N and get 2560N which rounds to 2.6 x 103N.
Signs are never irrelevant! They tell you which direction (with respect to your chosen coordinate system) things are acting or moving.
By the way, the answer should be 2.6 x 103N

Thanks :D

Can you list all the forces acting on the car and their directions? Draw a free body diagram.
 

Thread 'Errors and significant figures'

I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
View full post »
Thread 'A cylinder connected to a hanging mass'

Thread 'A cylinder connected to a hanging mass'

Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
View full post »

Similar threads

How Do You Calculate Frictional Force in a Braking Scenario?
Replies
2
Views
1K
Do the rail cars move on a 0.499% grade without brakes or external force?
Replies
12
Views
1K
Kinematics car braking scenario
Replies
8
Views
3K
Calculating max acceleration of a Tesla car
Replies
11
Views
3K
How Do You Calculate Race Car Acceleration and Power Output?
Replies
20
Views
2K
How far does the block slide? (work, spring, incline)
Replies
4
Views
2K
How Do You Calculate Component Forces in an Automotive Drum Brake?
Replies
3
Views
1K
How Far Will a Car Travel Before Stopping Without ABS at 115.2 km/h?
Replies
5
Views
2K
Calculating how a car consumes energy (gasoline)
Replies
8
Views
838
Coefficient of kinetic friction between a car and the road
Replies
12
Views
4K

Hot Threads

Recent Insights

Back
Top