Answer: 13.2 seconds.
Explanation: using equation of motion; S= ut +1/2at² where u = initial velocity=0
S= distance travelled
a = acceleration due gravity
t= time.
1 foot = 0.305m so,
S= 2860 feet =872.3m
S= ut+1/2 at²
872.3 = 0×t + 1/2×10 × t²
872.3 =0 + 5t²
T²= 872.3/5
T²= 174.46
Take the square root of T we then have;
t = 13.2 seconds to one decimal place.
Answer:
A.B = -38
Explanation:
A = 2i + 9j and B = -i - 4j.
So, A.B = (2i + 9j).(-i - 4j)
= 2i.(-i) + 2i.(-4j) + 9j.(-i) + 9j.(-4j)
= -2i.i - 8i.j - 9j.i - 36j.j
since i.i = 1, j.j = 1, i.j = 0 and j.i = 0, we have
A.B = -2(1) - 8(0) - 9(0) - 36(1)
A.B = -2 - 0 - 0 - 36
A.B = -38
Gravitational force decreases with increasing distance. So it decreases!
The work done by the gravitational force = 0
Given the mass of the box = 40 kg
The box is initially at rest.
Distance moved by the applied force = 5m
Force applied = 130 N
Co-efficient of friction between the box and floor = 0.3
The box is moved only in the horizontal direction by the applied force.
Gravitational force is applied in a direction perpendicular to the applied force. hence it doesn't do any work on the box.
Therefore, the work done by the gravitational force is zero.
Learn more about the gravitational force at brainly.com/question/862529
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