Before you can use Newton\'s Second Law to sum up the forces on an object, you f
ID: 1518707 • Letter: B
Question
Before you can use Newton's Second Law to sum up the forces on an object, you first need to know what forces are acting on that object. The technique is to draw a freebody diagram. This is a drawing of just that one body ("free" from all other objects), which only shows the forces (vectors) that act on it. Label the forces (draw the vectors and give the force a name like "F_gp -the force of the ground on person") on the object mentioned in the cases described below. Be sure to show the correct relative sizes of the force vectors. A person standing still on level ground. A person in an elevator that is accelerating upwards. A person running (accelerating) to the right. A person in an elevator that is accelerating downwards. A front-wheel drive car driving at constant speed on level ground. A person in an elevator that is moving upwards at a constant speed. A skydiver with her parachute open, drifting down at constant velocity. A car at rest on a hill. A lamp sitting on a book which is sitting on a table. A car accelerating up a hill.Explanation / Answer
1) Person standing still on level ground,
net F = 0,
Normal force acting up
Weight acting down.
2)
Normal Force acting up
Gravity acting down
Force of friction acting backward(to the left)
Acceleration force acting forward(to the right)
3)
driving force acting forward
Force of friction acting backward(to the left)
air resistance acting backward
4)
Weight (mg) acting downward
Drift force acting upward
5)
Normal force up
Weight Down
Force Down
6)
Fnet = F - mg = ma
W = mg+Mg down
Normal force up
accelartion force up
7)
W = mg down
Normal force up
accelartion force down
8)
W = mg+Mg down
Normal force up
9)Static friction
10)
WsinTheta acting downwards inclined
W acting down
WCosTheta acting downwards inclined
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