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mechanics doubt AS

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halosh92:
A car and a motorbike are at rest adjacent to one another at a set of traffic lights on a long,
straight stretch of road. They set off simultaneously at time t = 0. The motorcyclist accelerates
uniformly at 6 m s-2 until he reaches a speed of 30 m s-1 which he then maintains. The car
driver accelerates uniformly for 9 seconds until she reaches 36 m s-1 and then remains at this
speed.
(a) Find the acceleration of the car. (2 marks)
(b) Draw on the same diagram speed-time graphs to illustrate the movements of both
vehicles.
(4 marks)
(c) Find the value of t when the car again draws level with the motorcyclist. (7 marks)

halosh92:
2) A non-uniform plank AB of mass 20 kg and length 6 m is supported at both ends so that it is
horizontal. When a woman of mass 60 kg stands on the plank at a distance of 2 m from B, the
magnitude of the reaction at A is 35g N.
(a) Suggest a suitable model for
(i) the plank,
(ii) the woman. (2 marks)
(b) Calculate the magnitude of the reaction at B, giving your answer in terms of g.
(2 marks)
(c) Explain briefly, in the context of the problem, the term ‘non-uniform’. (2 marks)
(d) Find the distance of the centre of mass of the plank from A. (4 marks)

Kukkr:
I'll try to solve the questions but remember I didn't have M1 in AS... I only studied first few chapters of M1 in A2

Kukkr:

--- Quote from: halosh92 on March 08, 2010, 05:21:47 am ---(a) Find the acceleration of the car. (2 marks)

--- End quote ---
Answer:-
v=u+at
36=0+a(9)
36=9a
a=4m/s/s

Kukkr:

--- Quote from: halosh92 on March 08, 2010, 05:21:47 am ---A car and a motorbike are at rest adjacent to one another at a set of traffic lights on a long,
straight stretch of road. They set off simultaneously at time t = 0. The motorcyclist accelerates
uniformly at 6 m s-2 until he reaches a speed of 30 m s-1 which he then maintains. The car
driver accelerates uniformly for 9 seconds until she reaches 36 m s-1 and then remains at this
speed.
(a) Find the acceleration of the car. (2 marks)
(b) Draw on the same diagram speed-time graphs to illustrate the movements of both
vehicles.
(4 marks)
(c) Find the value of t when the car again draws level with the motorcyclist. (7 marks)

--- End quote ---
do you really have a problem with part B? I can solve it but its going to be a lot of work for a simple thing x_x

Answer(c):-
Use the graph!

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