KINEMATICS PROBLEMS

#2

YOUR NAME:

1.

Can an object move if there is no net force on it? Explain.

2.

Suppose you apply a force of 1

N to block A and a force of 2

N to block B.

Does it follow that block B has twice the acceleration of block A? Justif

y your

answer using Newton's second law.

3. When a brick rests on a flat, stationary, horizontal table,

there is an upward

normal

force on it from the table. Explain why the brick does not accelerate

upward in response to this force.

4.

A rock

et in space can change course with its engines. Since in empty space

there is nothing for the exhaust gases to push on, how can it accelerate?

5.

An airplane of mass 2867

kg flies at a constant horizontal velocity. The force

of air resistance on it is 2225

N. What is the net force on the plane

(magnitude and direction)?

6.

Three children are pulling on a toy that has a mass of 1.25

kg. Child A pulls

with force (5.00,

6.00,

2.50)

N. Child B pulls with force

(0.00,

9.20,

2.40)

N. With what force must Child C

pull for the toy to

remain stationary?

7.

(a) How much does a 70.0

kg person weigh on the Earth? (b) How much

would she weigh on the Moon (

g

moon

=

0.166

g

)? (c) How much would she

weigh on a neutron star where

g

star

=

1.43×10

11

g

?

8.

A dog on Earth weighs 1

36

N. The same dog weighs 154

N on Neptune. What

is the acceleration due to gravity on Neptune?

9.

When empty, a particular helicopter of mass 3770

kg can accelerate straight

upward at a maximum acceleration of

1.34

m/s

2

. A careless crewman

overloads the h

elicopter so that it is just unable to lift off. What is the mass of

the cargo?

10.

A 0.125

kg frozen hamburger patty has two forces acting on it that determine

its horizontal motion. A 2.30

N force pushes it to the left, and a 0.800

N

force pushes it to th

e right. (a) Taking right to be positive, what is the net

force acting on it? (b) What is its acceleration?

11.

A flea has a mass of 4.9×10

−7

kg. When a flea jumps, its rear legs act like

catapults, accelerating it at 2400

m/s

2

. What force do the flea's legs have to

exert on the ground for a flea to accelerate at this rate?

12.

An extreme amusement park ride accelerates its riders upward from r

est to

50.0

m/s in 7.00 seconds. Ignoring air resistance, what average upward force

does the seat exert on a rider who weighs 1120

N?

13.

A giant excavator (used in road construction) can apply a maximum vertical

force of 2.25×10

5

N. If it can vertically acc

elerate a load of dirt at 0.200

m/s

2

,

what is the mass of that load? Ignore the mass of the excavator itself.

14.

A tennis player strikes a tennis ball of mass 56.7

g when it is at the top of the

toss, accelerating it to 68.0

m/s in a distance of 0.0250

m. What is the

average

force the player exerts on the ball? Ignore any other forces acting on

the ball.

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