8. Two balls with different masses travel towards each other on a horizontal, fr
ID: 1865578 • Letter: 8
Question
8. Two balls with different masses travel towards each other on a horizontal, frictionless surface with equal speeds. Ultimately, they collide and stick together. All forces other than the forces of collision can be neglected. Which is a true statement:
a.)T or F Momentum is conserved.
b.)T or F Kinetic energy is conserved.
c.)T or F The final speed of each object is zero.
d.)T or F The final total kinetic energy is zero.
7. Two constant forces F1 = -3 N i and F2 = 4 N j, are the only ones acting on an object of mass 2 kg. What is the net work done on the object as it moves from a point with (x,y) coordinates (7m, 8m) to another with coordinates (9m, 8m)?
a.) 0 J
b.) -6J
c.) 6 J
d.) -10 J
e.) 10 J
f.) Cannot be determined
6. A Hooke’s Law spring of spring constant 4900 N/m is compressed by 0.02 m. This spring is used to fire a 0.050 kg ball directly upwards. How high does the bullet go (relative to its position when the spring was compressed)? Neglect air friction and other similar complications
a.) 1 m
b.) 2 m
c.) 4m
d.) 8m
5. During a snow storm, the roads are covered with frictionless ice. A car-1 of mass 2000 kg traveling at a speed of 6 m/s slams into a stationary car-2 of mass 1000 kg. The bumpers lock together and the car-2 and car-1 move together at a common velocity into the intersection after the collision. What’s the speed?
a.) 6 m/s
b.) 4 m/s
c.) 3 m/s
d.) 2 m/s
4. A hula-hoop of mass M and radius R is at rest at the top of an inclined plane as shown below. The hula-hoop rolls down the plane without slipping. When the hula-hoop reaches the bottom, its angular momentum around its center of mass is:
a.) M*R
b.) ½ M*R
c.) M
d.) M*g*h
e.) ½ M*g*h
3.) A cylinder of moment of inertia 4 kg. mass-2 about a fixed axis initially rotates at 80 radians/second about this axis. A constant torque is applied to slow it to 40 radians/sec. The kinetic energy lost by the cylinder is:
a.) 80 J
b.) 800 J
c.) 4000 J
d.)9600 J
e.) 19200 J
2. In problem 4, if the cylinder takes 10s to each 40 rad/sec, the magnitude of the applied torque is:
a.80 nm
b.40 Nm
c.32 Nm
d.16 Nm
e.8 Nm
1. A uniform rod of length 10 meters and mass 20 kg is balanced on a fulcrum. A mass of 40 kg is one end of the rod and a 20 kg mass is at the other end. How far is the fulcrum located from the center of the rod?
a.0m
b.1m
c.1.25m
d.1.5 m
e.2m
Explanation / Answer
8.
a. True,momentum of system is conserved
b. False, kinetic energy isn't conserved as the collision is perfectly inelastic.
c. False, as both the object havesome value of kinetic energy, hence velocities of objects can't be zero.
d. False.
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7.
Net force, F= -3i+4j
Position, x= (9-7)i+(8-8)j= 2 i
Work done, W= (-3i+4j).( 2i)= -6 J
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6.using energy conversation
Potential energy stored in spring= max gravitational potential
0.5* kx^2= mgh
h= 0.5* 4900*0.02^2/(0.05*9.8)
h= 2 m.
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5.
Using conservation of momentum
m1v1+m2v2= (m1+m2)V
2000*6+0= (2000+1000)v
v= 4 m/s
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Plz post other problem separately.
Comment in case any doubt..goodluck
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