If a block is sliding at constant speed across a frictionless surface, which of the following can we say is true? Explain why. a. There are no forces acting on the block in the vertical direction. b.The net for on the block is zero. c. There are no forces acting on the block in the horizontal direction. d. The block has a positive acceleration.

7. You put a box on a skateboard and give it a quick push with a certain force. It starts to move. After it leaves your hand, it will... * a. Continue at a constant speed forever. O b. Slow down constantly until it stops. c. Speed up constantly forever. d. Speed up for a little while, then go at a constant speed forever. e. Speed up for a little while, go at a constant speed for a while, then slow down to a stop. sheet of oa

A box is being pulled across a level floor by a rope attached to the box The rope is pulling partly upward at an angle of 30 degrees to the horizontal. In this circumstance A. The normal force between the box and the floor is greater than the weight of the box. B. The normal force between the box and the floor is less than the force of gravity on the box. C. The normal force between the box and the floor is the same as the force of gravity on the box. D. Which of the above is correct depends on whether or not the box is accelerating. E. Which of the above is correct depends on whether or not there is friction between the box and the floor. F. None of the above answers is correct.

The coefficient of kinetic friction is equal to the force of kinetic friction divided by   a. the normal force b. the weight of the object c. the mass of the object d. the acceleration of the object     Why is static friction more complex in analysis than kinetic friction? a .Because its magnitude and direction can vary b. Because it is invisible c. Because it does not depend on the normal force d. Because it depends on the kinetic friction

1.

Explain Newton's second Law and solve related problems Given a block which is at rest on a perfectly flat smooth table. You push with your hand horizontally on the block with some force. If the mass of the block = 2.00 kg and the acceleration of the block = 5.00 m/s2 then what is the force on the block from your hand in SI units?   a. 2.50 N   b. 0.100 N   c. 0.400 N   d. 10.0 N   e. zero

You push a lawnmower (mass=15kg) across the lawn at constant speed. To do so, you must excert 200 N of force. The handle makes a 35° angle with the horizontal.  A. Draw the force diagram B. What is the x-component of the force you apply? C. How does it compare to the frictional force which opposes your effort? Explain. D. If the frictional force is reduced to 100 N, determine the acceleration of the lawnmower.

2. A 10. Kg box pulled with a 40. N force at an angle of 20. degrees above the horizontal. The coefficient of kinetic friction is 0.20. Note it is moving along the table top. a) Draw a FBD showing all forces and the components of the pulling force. b) Determine the normal force. c) Determine force of friction acting on the box. d) Determine the acceleration of the box. e) Assume the box started from rest and was pulled for 2.0 seconds. Then the pulling force was removed. (i) Find the speed of the box after the 2.0 seconds. (ii) Determine how long it took for the box to come to rest after the pulling force was removed. 10kg -> 40N <200

A 10-kg wooden box rests on a ramp that is lying flat. The coefficient of static friction is 0.50, and the coefficient of kinetic friction is 0.30. What is the friction force between the box and ramp if a 30 N horizontal force is applied to the box? A.50 N B.20 N C.0 N D.30 N

14. A 150 kg motorcycle starts from rest and accelerates at a constant rate along a distance of 350m. The applied force is 250 N and the coefficient of kinetic friction is 0.03. a. Draw a free-body diagram for the motorcycle showing all applied forces to scale. Next to that diagram show the direction of the acceleration; b. Find the net force applied to the motorcycle; c. Find the acceleration of the motorcycle; d. What is its speed at the end of 350 m? e. Find the elapsed time of this acceleration.