Use g = 10.0 m/s2

Forces Review Game

Question #1A skydiver is descending with a

constant velocity. Consider air resistance. Diagram the forces acting upon the skydiver.

Question #1 - SolutionA skydiver is descending with a

constant velocity. Consider air resistance. Diagram the forces acting upon the skydiver.

Question #2A football is moving upwards

towards its peak after having been booted by the punter. Diagram the forces acting upon the football as it rises upward towards its peak. Assume no air resistance.

Question #2 - SolutionA football is moving upwards

towards its peak after having been booted by the punter. Diagram the forces acting upon the football as it rises upward towards its peak.

Question #3A car is coasting to the right and

slowing down. Diagram the forces acting upon the car.

Question #3 - SolutionA car is coasting to the right and

slowing down. Diagram the forces acting upon the car.

Question #4A rightward force is applied to a

book in order to move it across a desk at constant velocity. Consider frictional forces. Neglect air resistance. Diagram the forces acting on the book.

Question #4 - SolutionA rightward force is applied to a

book in order to move it across a desk at constant velocity. Consider frictional forces. Neglect air resistance. Diagram the forces acting on the book.

Question #5You are standing in the middle of a

crowded bus with standing room only. The driver suddenly brakes and you go flying forward into the arms of the person in front of you. Give your best geeky apology to the kind, handsome person who caught you, explaining to them exactly what happened.

Question #5 - SolutionANSWER: I am SO sorry. You see,

according to Newton’s First Law, an object in motion will remain in motion until acted upon by a net external force. I was in motion when the bus slammed on its brakes. Because of my inertia, I continued in the same state of motion until you applied a force to me to slow me down. Thank you very much!

Question #6Suppose that a sled has an

acceleration of 2 m/s2. If the net force is tripled, then what is the new acceleration of the sled?

Question #6 - SolutionSuppose that a sled has an acceleration

of 2 m/s2. If the net force is tripled, then what is the new acceleration of the sled?

ANSWER: Since ∑F = ma, acceleration and net force are directly proportional to each other. If the net force triples and the mass is kept the same, the acceleration must also triples. 6 m/s2

Question #7An elevator starting at rest on the

first floor accelerates upward at a rate of 2.0 m/s2. Find the normal force acting on a 75 kg person standing inside the elevator.

Question #7 - Solution An elevator starting at rest on the first floor accelerates upward at a

rate of 2.0 m/s2. Find the normal force acting on a 75 kg person standing inside the elevator.

Question #8 A box is sliding to the right and

encountering a friction force which slows it down. The coefficient of friction between the object and the surface is 0.1. Draw a FBD and find the acceleration. (Neglect air resistance.)

Question #8 - Solution A box is sliding to the right and encountering a friction force which

slows it down. The coefficient of friction between the object and the surface is 0.1. Draw a FBD and find the acceleration. (Neglect air resistance.)

Question #9Edwardo applies a 4.25-N

rightward force to a 0.765-kg book to accelerate it across a table top. The coefficient of friction between the book and the tabletop is 0.410. If the book starts at rest, how fast will it be going after 1.50 seconds have past?

Question #9 – Solution – Part A Edwardo applies a 4.25-N rightward force to a 0.765-kg book to

accelerate it across a table top. The coefficient of friction between the book and the tabletop is 0.410. If the book starts at rest, how fast will it be going after 1.50 seconds have past?

Question #9 – Solution – Part B Edwardo applies a 4.25-N rightward force to a 0.765-kg book to

accelerate it across a table top. The coefficient of friction between the book and the tabletop is 0.410. If the book starts at rest, how fast will it be going after 1.50 seconds have past?

Question #10A rightward force of 25 N is applied

to a 4.0 kg object to move it across a rough surface with a rightward acceleration of 2.5 m/s2. Draw a FBD and find the coefficient of kinetic friction between the object and the surface. (Neglect air resistance.)

Question #10 - Solution A rightward force of 25 N is applied to a 4.0 kg object to move it across

a rough surface with a rightward acceleration of 2.5 m/s2. Draw a FBD and find the coefficient of kinetic friction between the object and the surface. (Neglect air resistance.)

Question #11Andy pushes 65 kg crate with a

horizontal force of 250 N across the physics portable at a constant velocity of 3.0 m/s. Trying to be helpful and knowing a bit of physics, Betty uses a rope to pull directly up on the box. The coefficient of static friction is 0.70 and the coefficient of kinetic friction is 0.50. Find Betty’s applied force.

Question #11 - Solution Andy pushes 65 kg crate with a horizontal force of 250 N across the physics

portable at a constant velocity of 3.0 m/s. Trying to be helpful and knowing a bit of physics, Betty uses a rope to pull directly up on the box. The coefficient of static friction is 0.70 and the coefficient of kinetic friction is 0.50. Find Betty’s applied force.