URGENT - Please answer the following general physics questions related to force

Question

URGENT - Please answer the following general physics questions related to force and motion:

Question 1 (4 points) Which of the following statements concerning Newton's first law is untrue? a) If an object is at rest, the net force acting on it is zero. b) If the net force acting on an object is non-zero, the object cannot move at a constant speed along a straight line. c) If an object is moving at a constant speed along a straight line, the net force acting on it can be non- zero d) If the net force acting on an object is zero, the object must be moving at constant velocity or at rest

Explanation / Answer

1) Correct statements are a),b),d). Because Newton's 1st law states that unless you apply a force a body at rest and a body moving with constant speed along a straight line will continue to do so. When there is a net non zero force acting on the body, it can not continue motion with constant speed along a straight line. The force causes the body to change direction or magnitude of speed.

2) By Newton's 2nd law, F = mass×acceleration

= (0.250×9.80) N = 2.45 N

Option (c).

3) We have, force,F = ma = kg×m/s^2

lb is the unit of force in fps system.

Newton, N are units of force in S.I. system.

But option (5) can not be a unit of force. So (5).

4) By Newton's 2nd law, F = ma = (15×0.2) = 3.0 N

Option (b).

5) Correct option is (4).

Acceleration = change in velocity/time interval

= (20 - 12)/8 = 8/8 = 1 m/s^2

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