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19

velocity, equals, zero (2), directly proportional, determine, divide, gravity,

inversely proportional, matter, multiply, acceleration

1. Determine the force necessary to give an object with a mass of 4 kg an

acceleration of 6 m/s

2

We know that force a) ……. mass times b) …… (F = ma). To calculate the force

we must c) ……. 4 kg by 6 m/s

2

and get 24 N.

2. A force of 2800 N is exerted on a rifle bullet with a mass of 0.014 kg. What

will be the bullet’s acceleration?

Acceleration is a) …… to the magnitude of force and b) …… ……. to the mass

of the object. To determine the bullet’s acceleration we must c) ……. 2.800 N

by 0.014 kg and get d) ……. m/s

2

.

3. What is the unbalanced force on a car moving with a constant velocity of 20

m/s (45 mi/h)

There is no change in a) ……. which means that the acceleration is b) ……. . It

also means that the force on a object is c) ……. .

4. What is the weight of a 6-kg package of nails?

Mass refers to the amount of a) …….. an object contains and weight is related to

the force of b) ……. . The acceleration due to gravity on the surface of the Earth

is equal to 9.8 m/s

2

. To c) … . we must multiply 6 kg by 9.8 m/s

2

to get 58.8 N.

13. Choose the right answer.

1. How does a rocket accelerate?

a) Rockets accelerate because the gases rushing out of the back of the engine

push against the ground or the atmosphere.

b) A rocket exerts a strong force on the gases, expelling them; and the gases

exert an equal and opposite force on the rocket, propelling it forward.

2. Can a person move a sled with a block of marble on it of a sled exerts an

equal and opposite force backward?

a) No matter how hard he pulls, the backward reaction force always equals his

forward force so the net (unbalanced) force must be zero. He’ll never be able

to move this load.

b) The man can accelerate forward. There are two forces that affect his forward

motion: (1) the force exerted on the person by the sled, pulling backward on

him, and (2) the horizontal force exerted on him by the ground. When the

ground pushes forward on the man harder than his sled pulls backward, the

man accelerates forward.

14. Read the problem. Look at the sketches and answer the questions. Use

the expressions: to be at rest, to act upward/downward, the net / the normal

(perpendicular to the common surface of contact) force on the box is … ., the

force exerted by the table / by your friend is … .

19 velocity, equals, zero (2), directly proportional, determine, divide, gravity, inversely proportional, matter, multiply, acceleration 1. Determine the force necessary to give an object with a mass of 4 kg an acceleration of 6 m/s2 We know that force a) ……. mass times b) …… (F = ma). To calculate the force we must c) ……. 4 kg by 6 m/s2 and get 24 N. 2. A force of 2800 N is exerted on a rifle bullet with a mass of 0.014 kg. What will be the bullet’s acceleration? Acceleration is a) …… to the magnitude of force and b) …… ……. to the mass of the object. To determine the bullet’s acceleration we must c) ……. 2.800 N by 0.014 kg and get d) ……. m/s2. 3. What is the unbalanced force on a car moving with a constant velocity of 20 m/s (45 mi/h) There is no change in a) ……. which means that the acceleration is b) ……. . It also means that the force on a object is c) ……. . 4. What is the weight of a 6-kg package of nails? Mass refers to the amount of a) …….. an object contains and weight is related to the force of b) ……. . The acceleration due to gravity on the surface of the Earth is equal to 9.8 m/s2. To c) …. we must multiply 6 kg by 9.8 m/s 2 to get 58.8 N. 13. Choose the right answer. 1. How does a rocket accelerate? a) Rockets accelerate because the gases rushing out of the back of the engine push against the ground or the atmosphere. b) A rocket exerts a strong force on the gases, expelling them; and the gases exert an equal and opposite force on the rocket, propelling it forward. 2. Can a person move a sled with a block of marble on it of a sled exerts an equal and opposite force backward? a) No matter how hard he pulls, the backward reaction force always equals his forward force so the net (unbalanced) force must be zero. He’ll never be able to move this load. b) The man can accelerate forward. There are two forces that affect his forward motion: (1) the force exerted on the person by the sled, pulling backward on him, and (2) the horizontal force exerted on him by the ground. When the ground pushes forward on the man harder than his sled pulls backward, the man accelerates forward. 14. Read the problem. Look at the sketches and answer the questions. Use the expressions: to be at rest, to act upward/downward, the net / the normal (perpendicular to the common surface of contact) force on the box is …., the force exerted by the table / by your friend is ….

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