How do I calculate the magnitude of initial acceleration?

In summary: I think the speed was 8 m/s, not 8 m/sec.Ok, thanks. But probably should answer as signed: -0.57m/s^2. I think the speed was 8 m/s, not 8 m/sec.In summary, the system in this problem consists of a bicycle and cyclist traveling at a constant velocity of 8 m/s along a horizontal road. The total resistive force acting on the system is 40 Newtons and the total mass is 70 kg. To calculate the useful power output of the cyclist, we use the equation P=Fv and get 320 Watts. When the cyclist stops pedaling, the system comes to rest and we need to calculate the magnitude of
  • #1
sarahin3d
1
0

Homework Statement


A system consists of a bicycle and a cyclist traveling at a constant velocity along a horizontal road.

The total resistive force acting on the system in 4.0N and its speed is 8.0 m/s. Calculate the useful power output of the cyclist.

The cyclist stops pedalling and the system comes to rest. The total mass of the system is 70kg.
i) Calculate the magnitude of the initial acceleration of the system.

Homework Equations



P=Fv
s=ut+1/2at

The Attempt at a Solution



Alright so I used P=Fv to find the useful power output and I think I got the answer to that right.
P=Fv
P=(40)(8)
P=320 W

I don't know how to calculate the magnitude of the intial acceleration of the system. I would think that since the velocity is constant that the acceleration would have a magnitude of 0. This question is a 2 mark problem so I don't think that that answer would be right.
 
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  • #2
sarahin3d said:
I don't know how to calculate the magnitude of the intial acceleration of the system. I would think that since the velocity is constant that the acceleration would have a magnitude of 0. This question is a 2 mark problem so I don't think that that answer would be right.
Hi sarahin3d, welcome to Physics Forums.

The velocity was constant while he was peddling. But for this part of the question it says that the cyclist stops peddling.
 
  • #3
Hi

use the formula of force

F=ma

F= 40 N
m=70 kg
a=?

40=70 a
a= 40/70 ==> 0.57ms-2
 
  • #4
gneill said:
while he was peddling
What was he selling?
 
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  • #5
haruspex said:
What was he selling?
Ha! Oops, that was a brainfart typo! o:)
 
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  • #6
sarahin3d said:
force acting on the system in 4.0N
sarahin3d said:
P=(40)(8)
Is it 4N or 40N?
 
  • #7
haruspex said:
Is it 4N or 40N?

it should be 40
 
  • #8
arst said:
it should be 40
How do you know? It was posted by @sarahin3d, who appears no longer to be a member. Have you seen the source of the question?
 
  • #9
haruspex said:
How do you know? It was posted by @sarahin3d, who appears no longer to be a member. Have you seen the source of the question?
Yeah, I have the same source of question. it is 40 Newtons
 
  • #10
arst said:
Yeah, I have the same source of question. it is 40 Newtons
Ok, thanks. But probably should answer as signed: -0.57m/s2.
 

1. How do I calculate the magnitude of initial acceleration?

The magnitude of initial acceleration can be calculated by dividing the change in velocity by the change in time. This can be represented by the equation a = (vf - vi)/t, where a is the acceleration, vf is the final velocity, vi is the initial velocity, and t is the time interval.

2. What units should be used for initial acceleration?

The units for initial acceleration are typically meters per second squared (m/s²) in the metric system or feet per second squared (ft/s²) in the imperial system. This represents the change in velocity per unit time.

3. Can initial acceleration be negative?

Yes, initial acceleration can be negative. This indicates that the object is slowing down, or decelerating, during its initial motion. A positive initial acceleration indicates that the object is speeding up, or accelerating, during its initial motion.

4. How do I know if my calculation for initial acceleration is correct?

You can check if your calculation for initial acceleration is correct by plugging the values back into the original equation and solving for a. If the calculated value matches your original answer, then your calculation is most likely correct.

5. What are some real-life examples of initial acceleration?

Some real-life examples of initial acceleration include a car accelerating from a stop sign, a roller coaster accelerating downhill, and a rocket launching into space. These all demonstrate an object's initial acceleration as it changes from a state of rest to a state of motion.

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