111.Nishant sir, please explain this!
A particle of mass m moves on x axis as follows:It starts at t=0 from x=0 and comes to rest at t=1 and x=1.If 'a' denotes the instantaneous accelaration of this particle then,
a) a can not remain +ve for all t in the interval(t=[0,1])
b) a cannot exceed 2 at any point in its path.
c) a must be >=4 at some points in its path.
d)a must change sign during the motion.
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10 Answers
39That "a" cannot remain positive for all t in the interval (0,1) is obvious. The particle comes to rest at x = 1. It needs a deceleration for that purpose.
To start the motion, a +ve acceleration will be required, and to stop it, a -ve acceleration. So acceleration changes sign during the motion.
The acceleration isn't uniform, so we can't apply any equations of motions as far as I can think..
1i also think its a) & d)
as the acceleration is instantaneous (i think) we cannot comment upon the value of this acceleration!!!!
1i think its answer is a,c and d.because when u draw the the v-t curve and and take acceleration constant fr half time and then constant deceleration fr another half time then u found that the slope of the graph is 4, when there is a constant accl .it can also exceed 4 when u take non-uniform acceleration. the area under the curve in v-t graph denotes the distance travelled and it should be 1 according to the question .
1ya...nothing can be predicted about d magnitude a.
a MIGHT be >=4 or a MIGHT not exceed 2.....
1a motoboat going downstream overcame a raft at a pion A;t=60min later it turned back and after some time passed the rat at adistance l=6km from pint a.find the flow velocity assuming the duty of the engine to constant.
1sorry , it's 3km/h mai 3 hi lihna cha raha tha wo galti se 30 ho gaya
solution- let river flow velocity be xkm/h and vel of motorboet be v km/h.
in 1hr dist travelled by raft is x km and dist travelled by motorboat is [x + v]km .now assume that the raft is at rest and after turning ,the motorboat comes upstream at a speed of {(v-x)+x}km/hr = v km/hr , acc to relative vel concept .now it has to cover v km because it is vkm ahead of raft ,when it is turning .so time taken=v/v hr =1 hr .therefore total time when they meet again is 1+1=2 hr . therefore river flow velocity is =6/2 km/hr = 3km/hr