12. The net force, F newtons, needed to push a block
along a horizontal surface is directly proportional
to the mass, m kg, of the block. When m = 5,F = 49.
(iv) Draw the graph of F against m.
Answers
Answer:
1
Step-by-step explanation:
11th
Physics
Motion in a Plane
Velocity
A force F = 5t is applied o...
PHYSICS
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Asked on December 27, 2019 by
Yugal Shete
A force F = 5t is applied on a block of mass 10 kg kept on rough horizontal surface (μ=0.5), in rest what is speed of the block at t = 20 s?
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ANSWER
Friction has more max value is μms=0.5×10×10=50N
So at t=10sec the block will start to move
with acceleration a=
10
5t−50
m/s
2
Speed dv=u+adt
u= initial speed = 0
⇒dv=adt ;
;dv is speed gained in small time interval at after t= 10 second
⇒∫
v=0
v=v
1
dv=∫
t=10
t=20
adt
⇒v
1
=
10
1
∫
10
20
(0.5t−5)dt=
10
1
{
2
0.5t
2
−5t}
10
20
⇒v
1
=
10
1
[0.25(20)
2
−5(20)−{0.25(10)
2
−5(10)}]
& v
1
=
10
1
[100−100−{25−50}]
⇒v
1
=2.5m/s
(i) F∝m f=km 49=k5 k=49/5 k=9 ⅘ k=9.8
Hence,the equation is f=9.8m
(ii) f=9 ⅘ m f=9 ⅘ (14) f= 49/5 (14) f= 686/5
Hence, f= 137.2
(iii) f =49/5m 215.6=49/5m m=215.6(5/49) m=22
(iv)open this below image
