Answer whether the following statements are true or false: e.g., if the first is

Question

Answer whether the following statements are true or false: e.g., if the first is true and the rest are false, enter TFFFFF. Assume all ropes are massless and cannot stretch. i. The magnitude of the normal force acting on an object is always equal to the weight of the object. ii. A man pulls up on the handle of a suitcase that is sitting on the floor, but he is unable to lift it. While he is pulling, the magnitude of the normal force of the floor on the suitcase is equal to the weight of the suitcase minus the magnitude of the pulling force. iii. A bucket of water is being pulled straight up by a rope. The speed of the bucket is increasing. The free body diagram for the bucket is correct. iv. A gymnast is sliding down a vertical rope attached to the ceiling. Her speed is decreasing. The magnitude of the tension in the rope is less than the magnitude of the gymnast's weight. v. A gymnast is climbing up a vertical rope attached to the ceiling. Her speed is increasing. The free body diagram for the gymnast is correct. vi. A man sits on top of a suitcase, which is silting on the floor. The magnitude of the normal force of the floor on the suitcase is greater than the weight of the suitcase.

Explanation / Answer

i. False

Reason: It is not always true that normal force equals to weight. For example if the object is pressed to the wall, in this case normal force is horizontal and not equal to the weight.

ii. False

Reason: Since the bundle of suitcase is not lifted, normal force in this case is = weight

iii. True

Reason: Since speed of the bucket s increasing in upward direction, net force is directed upward. Thus upwards force must has larger value than the downward force, hich is correct in the figure shown.

iv. False

Reason, Applying Newton’s 2nd law we get,

Fnet = ma

T-W=ma

Since speed is decreasing in the downward direction, acceleration is upward, positive.

T=ma+W

T > W

Which shows that Tension T is greater than W.

v.False

Reason, Applying Newton’s 2nd law we get,

Fnet = ma

T-W=ma

Since speed is increasing in the upward acceleration is upward, positive.

T=ma+W

T > W

Which shows that Tension T is greater than W.

Thus the FBD should be as below,

vi. True

Reason,

Applying Newton’s 2nd

Fn – W1 – W2 = ma =

Fn = W1+W2

Thus normal force = weight of suitcase + weight of man

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