Impulse: multiple choice question

In summary, the conversation is about solving a physics problem involving calculating the average acceleration of a car that comes to rest over a distance of 0.30 m with an initial speed of 10 m/s. The original estimate of the time for the collision was incorrect as it assumed zero acceleration. It is necessary to assume constant acceleration in order to solve the problem. SUVAT equations can be used to calculate the average acceleration.
  • #1
zanyzoya
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Hi all
Can anyone please help me with Q14 (attached) as you can see I am getting 167000N however the correct answer is 83000N
Many thanks
ZanyZoya
 

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  • #2
Your estimate of the time for the collision (t = d/v) is inappropriate. This equation is used if the acceleration is zero. Here this is clearly not the case. What is is the average acceleration of a car that comes to rest over a distance of 0.30 m when it has initial speed 10 m/s?
 
  • #3
Hmm we can’t use suvat equations as acceleration is not constant, we could use average acceleration =change in velocity/time but we don’t know time... hmm
 
  • #4
zanyzoya said:
Hmm we can’t use suvat equations as acceleration is not constant ...
You have to assume that the acceleration is constant, otherwise you cannot solve the problem. What you cannot assume is that the acceleration is zero, which is what you did initially. So yes, use the SUVAT equations.
 
  • #5
Thanks for your help kuruman, I think I’ve got it now.
 

1. What is impulse?

Impulse is a force that acts on an object for a short period of time, resulting in a change in the object's momentum.

2. How is impulse calculated?

Impulse is calculated by multiplying the force acting on an object by the time during which the force is applied.

3. What is the unit of impulse?

The unit of impulse is Newton-second (Ns) or kilogram-meter per second (kg·m/s).

4. How is impulse related to momentum?

Impulse is directly proportional to the change in momentum of an object. This means that the greater the impulse, the greater the change in momentum.

5. What are some real-life examples of impulse?

Some examples of impulse in everyday life include kicking a soccer ball, hitting a baseball with a bat, or jumping off a diving board. These actions involve a short force acting on an object, resulting in a change in momentum.

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