Momentum+Physics Question

  • Thread starter RajdeepSingh7
  • Start date
In summary, the conversation is about a question regarding a crash test program where cars are fitted with dummies and accelerated into concrete walls to record the effects on the occupants. The question involves calculating the momentum, impulse, and average force exerted on the car and one of the dummies in a collision. The last two questions ask about the impact of the car's front crumpling and the force exerted on a dummy who was not strapped in.
  • #1
RajdeepSingh7
9
0
Momentum+Physics Question :D

Hey Everyone.
This is a question which I have received and have completed to the best of my ability.
I was wondering if anyone would be willing to look over it too see if I was correct, and maybe aide me with the last two questions


The Question is:


In a crash test program, cars are fitted with dummies ( named Matt, Hugo and Fred ) which have similar characteristics and masses to humans. The cars are then accelerated and crashed into concrete walls with high speed camera recording the effects o the occupants of the vehicle. One such vehicle, a "Fasty" has a mass of 1200 kg and is accelerated from rest to 13.5 ms^(-1). The car is then brought to rest in a head on collision with a wall. The collision time was 80.0 milliseconds.

(a)

What is the momentum of the car before it collides with the wall?


Using,
p=mv

And Values:
m= 1200
v= 13.5

p=(1200)(13.5)
Momentum = 16200 kg ms^(-1)



(b)

What is the impulse exerted on the car by the wall?


Using,
Impulse = Change In Momentum

Initial Momentum = 16200 kg ms^(-1)
Final Momentum = (1200)(0)= 0 ms^(-1)

Therefore, Impulse = 16200-0= 16200 Newton Seconds

(c)What is the average force exerted by the car on the wall?

Using,
Average Force = Impulse/Change In Time
=16200/0.080
Average Force = 202500 Newtons.



(d) The front of the "Fasty", crumples on impact. How would the impulse and the force have compared if the front of the "Fasty" had not crumpled?
&
(e) One of the dummies, Fred (body mass 60kg), was not strapped into a seat belt. As a result of the collision with the wal, Jamie was projected through the windscreen and collides head first ino the wall. Use the data below to determine the force exerted on Jamie's Skull.

Estimates: Mass of Jamie's Skull = 5 kg
Collision Time = 0.5 Seconds


The following questions I am having trouble starting off, so If anyone could start them off for me it would be appreciated.

Any Help and correction will be greatly appreciated, and I will post any progress I make on the problem.
 
Physics news on Phys.org
  • #2
d) If the front of the "Fasty" had not crumpled, the impulse would have been greater as the time taken for the car to come to rest would have been longer. The force would have been lower as it would have been spread out over a longer time period.e) Using Impulse = Change in Momentum:Initial Momentum = 0 kg ms^(-1)Final Momentum = 5*v (where v is the velocity of Jamie's skull after the collision with the wall)Therefore, Impulse = Change in Momentum = 5*vUsing Average Force = Impulse/Change in Time= 5*v/0.5 Average Force = 10*v Newtons
 
  • #3


Hi there,

First of all, great job on solving the first three parts of the question! Your use of the momentum equation and impulse equation is correct.

For part (d), if the front of the "Fasty" had not crumpled on impact, the impulse and force would have been greater. This is because when the front of the car crumples, it absorbs some of the impact and slows down the car more gradually, resulting in a longer collision time. This means that the change in momentum is spread out over a longer period of time, reducing the overall force exerted.

For part (e), we can use the same equation for average force (F=Impulse/change in time) to calculate the force exerted on Jamie's skull. However, we need to first calculate the impulse on Jamie's skull. To do this, we need to find the change in momentum of Jamie's head.

Initial momentum = 60kg * 13.5 ms^(-1) = 810 kg ms^(-1)
Final momentum = 5kg * 0 ms^(-1) = 0 kg ms^(-1)

Therefore, change in momentum = 810 kg ms^(-1)

Now, we can plug this value into the impulse equation to find the impulse on Jamie's skull.

Impulse = change in momentum = 810 Newton Seconds

Finally, we can use the impulse and collision time to calculate the average force exerted on Jamie's skull.

Average Force = Impulse/Change in Time = 810/0.5 = 1620 Newtons

I hope this helps you with the remaining parts of the question. Keep up the good work!
 

1. What is momentum?

Momentum is a measure of an object's motion, taking into account its mass and velocity. It is a vector quantity, meaning it has both magnitude and direction. In simpler terms, momentum is the amount of force needed to stop an object in motion.

2. How is momentum calculated?

Momentum is calculated by multiplying an object's mass by its velocity. The formula for momentum is: p = m * v, where p is momentum, m is mass, and v is velocity. The units for momentum are kilogram-meters per second (kg*m/s).

3. What is the law of conservation of momentum?

The law of conservation of momentum states that the total momentum of a closed system remains constant. This means that in any interaction between two or more objects, the total momentum before the interaction is equal to the total momentum after the interaction, as long as there are no external forces acting on the system.

4. What is the difference between linear and angular momentum?

Linear momentum refers to an object's motion in a straight line, while angular momentum refers to an object's rotational motion around an axis. Linear momentum is affected by an object's mass and velocity, while angular momentum is affected by its moment of inertia and angular velocity.

5. How does momentum relate to force?

Momentum and force are related through Newton's second law of motion, which states that force is equal to the rate of change of an object's momentum. This means that the greater the force applied to an object, the greater its change in momentum will be. In other words, a larger force will cause an object to accelerate more quickly.

Similar threads

Replies
1
Views
488
  • Introductory Physics Homework Help
Replies
6
Views
627
  • Introductory Physics Homework Help
Replies
9
Views
2K
  • Introductory Physics Homework Help
Replies
2
Views
1K
  • Introductory Physics Homework Help
Replies
7
Views
1K
  • Introductory Physics Homework Help
Replies
9
Views
964
  • Introductory Physics Homework Help
Replies
3
Views
6K
  • Introductory Physics Homework Help
Replies
9
Views
2K
  • Introductory Physics Homework Help
Replies
3
Views
4K
  • Introductory Physics Homework Help
Replies
4
Views
2K
Back
Top