in preparation for Halloween, your instructor is preparing a scary falling house
ID: 1970389 • Letter: I
Question
in preparation for Halloween, your instructor is preparing a scary falling house decoration. A .750kg block of clay is attached to the bottom of k= 8.00N/m spring. The clay is released from rest, 1.3m above the ground, as an unsuspecting trick-or-treater walks up to doorway to receive their goodies.a. if the spring is unstretched when the clay is released, how fast is it going when it hits the ground? Ignore air resistance in your calculation.
b. After hitting the ground, the clay sticks to the floor. Assume the sticking force between the clay and the ground, Fclay, has the same direction as a normal force but can be either up or down. What magnitude and direction of Fclay is necessary to stop the clay's motion (with constant deceleration) in 0.500s?
c. If the clay is to stay attached to the floor, i.e. if its acceleration is to become zero when its speed becomes zero, what magnitude and direction of Fclay is needed? Assume this change in the clay's force is instantaneous.
Explanation / Answer
initial potential energy=mgh=0.750*10*1.3= 9.750J
potential energy stored in spring= 0.5 k x2 =0.5 *8 *1.3*1.3 =6.76J
energy remaining= 9.750-6.76 = 2.99J
this is purely kinetic,
0.5 m v2=2.99
v=2.82m/s.............(1)
if clay has to remain on floor
Fclay=k*x
Fclay= 10.4 N...........(3)
to stop it in 0.5 sec
V=0;
V=(A2-x2)
=(K-F/x
x=acos(0.5 sec)
using thi s we can find magnitude
direction is opposite to that of the spring force
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