Name: ______Score: _____/20
Self Assessment: Newton’s Laws of Motion
1. Define unbalanced forces. How can you tell by looking at an object if the forces on
it are unbalanced?
True or False. Explain.
2. ______When forces are balanced something does not move.
3. ______When forces are balanced something moves at a constant speed.
4. ______When forces are balanced something accelerates.
5. ______When forces are unbalanced something does not move.
6. ______When forces are unbalanced something moves at a constant speed.
7. ______When forces are unbalanced something accelerates.
8. Explain what inertia is and what other property of matter it depends on.
Use the formula F=ma to solve the following. Show your work! Don’t forget the correct
units and sig figs.
9. ______What is the acceleration of a truck with a mass of 1200 kg
moving because of a 7800 N force?
10. ______What is the mass of a soccer ball that is accelerating at
11.5 m/s/s because of an applied force of 167 N?
11. Earth is pulling me down. We call that gravity. If gravity is the action, what is the
equal and opposite reaction?
Identify which Law of Motion each is by placing a 1, 2 or 3 in the blank
12. ______You’re in a car that slams on the brakes and you go flying forward
13. ______When you hit a nail with a hammer, they both feel the same force
14. ______The nail in #2 moves more than the hammer does.
15. ______I can throw a baseball farther than a shotput.
16. ______When I throw the baseball, it would go straight, if it weren’t for gravity
and air resistance.
17. ______It takes more effort to push a full shopping cart than an empty one.
18. ______The weight of an object is its mass times the acceleration due to gravity.
19. ______I hit a ball with a bat. The same force is exerted on both objects.
20. ______I spin a yoyo in a circle. If I let go of the string, it flies off in a straight line.
Name: __Answer key__ Score: _20_/20
Self Assessment: Newton’s Laws of Motion
1. Define unbalanced forces. How can you tell by looking at an object if the forces on
it are unbalanced?
Total forces are not equal
The object accelerates (changes speed,
direction or both)
True or False. Explain.
2. __True*___ When forces are balanced something does not move.
* kinda. It can be not moving. But it is also
true that it can move with a constant speed.
A better way to put this is to say that when
forces are balanced something is not changing its motion. That is certainly true.
3. __True___ When forces are balanced something moves at a constant speed.
If the forces are balanced there is no change
in motion, so it keeps doing whatever it was doing.
4. __False___ When forces are balanced something accelerates.
It takes unbalanced forces to change motion
(accelerate) see Newton’s First Law of Motion.
5. __False___ When forces are unbalanced something does not move.
According to Newton’s First Law of Motion,
unbalanced forces lead to acceleration … motion.
6. __False___ When forces are unbalanced something moves at a constant speed.
According to Newton’s First Law of Motion,
unbalanced forces lead to acceleration (change in speed or direction or both).
7. __True___ When forces are unbalanced something accelerates.
Newton’s First Law of Motion says so.
8. Explain what inertia is and what other property of matter it depends on.
Tendency of an object to resist changes in
motion
Depends on mass. More mass = more inertia
Use the formula F=ma to solve the following. Show your work! Don’t forget the correct
units and sig figs.
9. _6.5 m/s2_ What is the acceleration of a truck with a mass of 1200 kg
moving because of a 7800 N force?
F = ma 7800 = 1200 (a) (div. both sides by 1200)
a = 7800/1200
a = 6.5 (2 sig figs)
10. _14.5 kg _ What is the mass of a soccer ball that is accelerating at
11.5 m/s/s because of an applied force of 167 N?
F = ma 167 = (m) 11.5 (div. both sides by 11.5)
m = 167/11.5
m = 14.521739813 (3 sig figs)
11. Earth is pulling me down. We call that gravity. If gravity is the action, what is the
equal and opposite reaction?
You are pulling back on the Earth! (Why doesn’t the Earth move then? Well, technically it does, but not a whole lot because it has more inertia)
Identify which Law of Motion each is by placing a 1, 2 or 3 in the blank
12. ___1___ You’re in a car that slams on the brakes and you go flying forward
13. ___3___ When you hit a nail with a hammer, they both feel the same force
14. ___2___ The nail in #2 moves more than the hammer does.
15. ___2___ I can throw a baseball farther than a shotput.
16. ___1__ When I throw the baseball, it would go straight, if it weren’t for gravity
and air resistance.
17. ___2___ It takes more effort to push a full shopping cart than an empty one.
18. ___2___ The weight of an object is its mass times the acceleration due to gravity.
19. ___3___ I hit a ball with a bat. The same force is exerted on both objects.
20. __1__ I spin a yoyo in a circle. If I let go of the string, it flies off in a straight line.