How much impulse is required to change the velocity of a 2500 kg truck by 15 m/s?
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Answer:
A car weighing 2500 kg and travelling at 15 m/s stops at a distance of 25 m deceleration uniformly. What is the force exerted on it by the brakes?
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5 Answers
Naren Nagarajan
, Cambridge Examinations Officer at Kasiga School, Dehradun (2008-present)
Answered 3 years ago · Author has 1.1K answers and 1.9M answer views
(a) W= Fd ( energy = force x distance )
(b) KE = .5 m v*v ( Kinetic energy of the car )
KE =0.5 * 2500 * 225KE =281250 Joules
Using (a) , Reducing kinetic energy to zero over 25 m
281250 = F * 25
F = 281250 /25
F = 11250 N
To check or use a different method …..
v^2 = u^2 +2as ( Third equation of motion )
2as = v^2 -u^2 ( v = 0 and U = 15 )
as = -225/2
a = - 225/2 * 25
a= - 225/50
a= - 4.5 m sec ^ -2
F = ma
F = 2500 * - 4.5
F = - 11250 N ( the negative sign indicates that the force is opposite in direction to the motion of the car )
The answer is correct since both values for F are equal.
If this is homework help , Read the textbook, watch a video and don’t ask for answers for homework on Quora.
Ideally I should have expounded everything related to force, motion and energy to you but sadly, I lack the patience to type so much.