1) A force F = (80, -90) N acts on a mass of 7 kg . At time t = 0 s , the mass h
ID: 1769067 • Letter: 1
Question
1) A force F = (80, -90) N acts on a mass of 7 kg. At time t = 0 s, the mass has a velocity v0 = (-5, -4) m/s.
What are the (x,y) components of the velocity vector (in m/s) after 4 seconds?
2) Block 1 (10 kg) is located on the surface of a table. A rope pulls on block 1 with a tension of 82.00 N at an angle of 77.31 degrees above the horizontal. The coefficient of kinetic frictionbetween the block and the surface equals 0.4.
On a sheet of paper, draw the free body diagram for block 1 using the two-subscript notation from class. After completing the free body diagram, enter below each force and its x & y-components. Remember that the x-component is the "i" component and the y-component is the "j" component.
FORCES on BLOCK 1
Weight force on block 1 by Earth
W1E = i + j N
Tension force on block 1 by Rope (rounded to nearest integer)
T1R = i + j N
Normal force on block 1 by Surface
N1S = i + j N
Frictional force on block 1 by Surface
f1S = i + j N
What is the acceleration a of block 1?
a = i + j m/s2
3)
A ball of mass 2.1 kg hangs at the end of a string 1.1 m in length from the ceiling of a room. The height of the room is 3.6 m. What is the gravitational potential energy of the ball relative to the ceiling?
What is the gravitational potential energy of the ball relative to the floor?
What is the gravitational potential energy (in J) of the ball relative to a point at the same elevation as the ball?
Tries 0/2Explanation / Answer
1)
a = (11.43 , -12.86 )
V = ( 40.72 , -55.44 ) = ( vx , vy)
2)
N = mg - Tsin77.3
N = 18.006 N
82cos77.31 - 0.4*18.006 = 10*a
a = 1.0824 m/s^2
3)
wrt to ceiling
=2.1*9.8*(-1.1) = -22.638 J
with floor
=2.1*9.8*(3.6-1.1) = 51.45 J
with same level = 0 J
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