# Dynamics

1500 kg automobile is traveling up to 20 degree incline at a speed of 6 m/s. if the driver wishes to stop his car in a distance of 5m, determine the frictional force at pavement which must be supplied by rear wheels

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1. A body is said to be perfectly elastic, if it returns back___________

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2. The kinetic energy of the car will be dissipated as heat due to the frictional forces.
KE=(1/2)mV^2=1500*36/2=27000 J

The work done by frictional forces=F*d
Now, F*d=KE
F=KE/d=27000/5=5400 N

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3. m=1500 kg; α =20º; s=5 m

KE=W(fr)+PE.

KE=m•v²/2;
W(fr) =F(fr) •s
PE=m•g•h=m•g•s•sinα.

m•v²/2 = F(fr) •s+ m•g•s•sinα;
F(fr)= m{ v²/2 - g•s•sinα}/s =
= 1500{36/2 -9.8•5•0.342}/5 =372.6 N
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The body is perfectly elastic if after being deformed under the action of an external applied force the body completely returns to its initial condition on the removal of the force.

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4. true or false
a)a rigid body is an idealization of the behaviour of a body.
b)A GEO stationary satelite follows a circular orbit at a unique and has a time period of 24th.
c)constancy of areal velocity for a central force motion of a particle does not imply that the angular momentum is conserved
d)every planet moves in an orbit which is an ellipse with the sun at one focus
e)for perfectly elastic central impact the two bodies must move stuck together onlu if the impact is direct

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5. fill in the blanks----
a)the power developed by a force is ______ and that of couple is _______.
b)the velocity of cylinder which is released from rest on 0 degree incline after it has rolled through a distance l is given.
c)the conditions for non slipping is_______.
c)the direction of coriolis acceleration is obtaind by ______.
d)the action of a spring on a movable body to which it is attached is a common example of ________.

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6. true or false
a)a rigid body is an idealization of the behaviour of a body.
b)A GEO stationary satelite follows a circular orbit at a unique and has a time period of 24th.
c)constancy of areal velocity for a central force motion of a particle does not imply that the angular momentum is conserved
d)every planet moves in an orbit which is an ellipse with the sun at one focus
e)for perfectly elastic central impact the two bodies must move stuck together onlu if the impact is direct

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2. 👎 0

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