Transcript Forces Review Game

Forces Review Game
Use g = 10.0 m/s2
Question #1
 A skydiver is descending with a constant velocity.
Consider air resistance. Diagram the forces acting
upon the skydiver.
Question #1 - Solution
 A skydiver is descending with a constant velocity.
Consider air resistance. Diagram the forces acting
upon the skydiver.
Question #2
 A 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 - Solution
 A 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 #3
 A car is coasting to the right and slowing down.
Diagram the forces acting upon the car.
Question #3 - Solution
 A car is coasting to the right and slowing down.
Diagram the forces acting upon the car.
Question #4
 A 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 - Solution
 A 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 #5
 You 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 - Solution
 ANSWER: 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 #6
 Suppose 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 - Solution
 Suppose 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 #7
 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 #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 #9
 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 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 #10
 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 #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 #11
 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.
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.