Download Forces and Newton`s Laws Quiz Self

G
Name ________________________________
r
Forces and Newton’s Laws Quiz Self-Testing Guide 2016
Per. ___
a
v
~Due day of the quiz~ ANSWERS IN BOLD
i
Students should be able to . . .
t
Forces – remember when we hit a ping pong and bouncy balls with a popsicle
y stick to
understand different forces.
1. Draw all the force arrows for the forces acting on a boy pulling a wagon.
2. What do you call a force that moves something in a circle?
Push
A centripetal force will keep something moving in a circle.
Air Res.
Friction
Newton’s Laws – remember when we used the coat hanger and tennis balls to show 1st law,
did the sled races for 2nd law and used spring scales to show equal and opposite forces for
3rd Law?
3. Put the list of objects in order from least inertia to greatest inertia: cell phone, milk cow, pencil,
student, textbook.
Inertia is an object’s resistance to a change in motion; like how easy or difficult it is to get
an object at rest to move. In order of least to greatest: pencil, cell phone, textbook,
student, milk cow.
4. Which has more inertia a penny or a quarter? How could you do a test to prove it?
A quarter has more inertia than a penny because it has a higher mass. You can test this
by sliding a penny at a quarter, and then sliding a quarter toward a penny. Whichever
coin moves the farthest after being hit has the LOWEST inertia.
5. Describe Newton’s 1st Law of motion
You can describe Newton’s first Law without defining it by explaining that an
unbalanced force is required to either create or change motion.
6. How does the force needed to move a desk relate to Newton’s 1st Law
The force needed to move a desk is defined as an unbalanced force by Newton’s 1 st Law.
When forces are balanced the object is either at rest or moving steadily.
7. When you kick a soccer ball, is that an example of balanced or unbalanced forces on the ball.
If the soccer ball moves when you kick it, the force you added has to be unbalanced
because motion was created. The balanced forces on the ball kept it still until you added
8. Use Newton’s 1st Law to describe why Kimberly suddenly shifts to the right when riding in a car that
suddenly turns left.
Newton’s 1st Law states that Kimberly wants to keep moving in the same direction (stay
in motion). So when the car changes direction, Kimberly tries to keep going straight, this
makes her appear to move to the right as the car moves left.
9. Can Newton’s 1st Law be described by a formula?
No. There is no formula for Newton’s 1st Law or for inertia. We just know that inertia
increases as mass increases.
10. If Andrea is riding a bike at a steady pace, is there an unbalanced force acting?
For an unbalanced force to be acting there would need to be a change in motion. If the
bike is going at a steady speed, then there are no unbalanced forces.
11. What is the formula for Newton’s 2nd Law?
F = ma where F = force, m = mass, and a = acceleration.
F
mxa
12. What formula would you use to find acceleration if you know the mass and force? What formula
would you use to find mass if you know the acceleration and force applied?
Based on the “force square”, to find acceleration use a = F/m. To find mass use m = F/a.
13. If the force is constant, will a 10 kg or a 5 kg object have the greatest acceleration? How do you know?
For a set force, the high mass object (10kg) will have less acceleration because it takes more force
to move a larger mass.
14. What direction will the friction force point for a hockey puck on ice? How do you know?
The object will move to the right because the object always accelerates in the same direction as
the force that was applied
15. What force would be required to accelerate a 10 kg cart at 2 m/sec2? SHOW YOU WORK!
F = ma
F = (10 kg)x(2 m/sec2)
F = 20 kg * m/sec2 - A Newton is a kg * m/sec2
F = 20 Newtons
16. If a 100 g ball is accelerating down the hill at 5 m/sec2, what is the size of the force causing the
acceleration? SHOW YOU WORK!
F = ma F = (100 g)x(5 m/sec2)
F = 500 g m/sec2 - but for Newtons we need kg m/sec2
F = 0.500 Newtons (Note that we didn’t start with kg which are the standard for a
Newton)
17. Kiahra pushed a 5 kg box of dance flyers with a force of 10 N. What is the acceleration of the box?
SHOW YOU WORK!
So a = F/m
a = 10 N/ 5 kg
a = 2 m/sec 2
F
mxa
18. What mass can Kevin accelerate to 5 m/sec 2 using a 10 N force? SHOW YOU WORK!
So m= F/a
m= 10 N/ 5 m/sec 2
m= 2 kg
F
mxa
19. Describe Newton’s 3rd Law.
For every action force, there is an equal and opposite reaction force is Newton’s 3 rd Law
20. Describe the action and reaction FORCES when you kick a ball.
When you kick a ball, your foot puts an action force on the ball, and the ball put a reaction force
onto your foot.
21. What is the difference between action/reaction forces and balanced/unbalanced forces acting on an
object?
Action/reaction force pairs act on DIFFERENT objects. Balanced/unbalanced forces
focus on the forces acting on a single object. Balanced/unbalanced forces determine if
the object will be in motion.
22. If I apply a push force to one of the moveable demo tables, what is the size and direction of the force it
applies to my hand?
When I apply a force on the moveable demo table, the table exerts a force on my hand
that is equal in size, but opposite in direction.
23. Can a reaction force ever be greater or less than an applied force?
NO. Newton’s 3rd Law says the reaction force must be equal in size, and opposite in
direction compared to the action force.
24. What’s the relationship between mass and weight?
Weight is the force of gravity pulling on the object. Mass is the amount of matter of the object.
25. Define how each of Newton’s Laws applies to Marissa kicking a soccer ball or a car moving away from a
stop light.
According to Newton’s 1st Law, the soccer ball will move if Marissa applies an unbalanced force.
According to Newton’s 2nd Law a soccer ball will accelerate more than a basketball because the
soccer ball has less mass. According to Newton’s 3rd Law, when Marissa applies a force to the soccer
ball with her shoe, the ball also applies an equal and opposite reaction force to her shoe!
According to Newton’s 1st Law, the force that a car motor applies to move it away from a stop light
must be large enough to unbalance all the other forces around. According to Newton’s 2nd Law, the
acceleration created will increase with the size of the force and decrease as the mass of the car
increases. The force that the motor puts on the axel to move the car is equal and opposite to the
force that the axel puts back on the motor.