Review of
Projectile Motion,
Mass & Weight
What is the weight of a 50 kg object
near Earth?
Ans. 500 N
What is the mass of a 5 kg rock on
the Earth?
Ans. 5 kg
What is the
weight of a
10 kg rock
on the
Moon?
(g = 1.7 m/s2)
Ans. 17 N
What is the acceleration?
80
70
60
50
Velocity
40
(m/s)
30
20
10
0
0
1
2
3 4 5
Time (s)
6
7
8
Ans. 20 m/s2
If the object has a mass of 2 kg,
what is its weight?
80
70
60
50
Velocity
40
(m/s)
30
20
10
0
0
1
2
3 4 5
Time (s)
6
7
8
Ans. 40 N
What is the displacement for the
first 5 seconds?
80
70
60
50
velocity
40
(m/s)
30
20
10
0
0
1
2
3 4 5
Time (s)
6
7
8
Ans. 75 m
A man throws a
ball vertically
upward. What is
its velocity at its
highest point?
Ans. zero
A man throws a
ball vertically
upward. What is
its acceleration at
its highest point?
Ans. 10 m/s2 downward
A man throws a
ball vertically
upward with an
initial speed of 25
m/s. At what time
does it return to his
hand?
Ans. 5 s
A man throws a
ball vertically
upward with an
initial speed of 25
m/s. How high
does it go?
Ans. 31.3 m
What is the displacement for the
first 3 seconds?
80
70
60
50
Position
(m)
40
30
20
10
0
0
1
2
3 4 5
Time (s)
6
7
8
Ans. 60 m
What is the acceleration?
80
70
60
50
Position
(m)
40
30
20
10
0
0
1
2
3 4 5
Time (s)
6
7
8
Ans. zero
What is the weight?
45 kg
Ans. 450 N on Earth
Planet X has an acceleration
due to gravity of 0.1 m/s2. Joe
can jump 1 m vertically on Earth.
How high can he jump on Planet
X?
Ans. 100 m
Planet X has an acceleration
2
due to gravity of 0.1 m/s . Joe
has a mass of 55 kg on Earth.
What is his mass on Planet X?
Ans. 55 kg
Joe can lift a mass of 136 kg on
Earth. How much weight is he
lifting?
Ans. 1360 N
Planet X has an acceleration
due to gravity of 0.1 m/s2. Joe
can lift a mass of 136 kg on
Earth. How much mass can he
lift on Planet X?
Ans. 13600 kg
Planet X has an acceleration
due to gravity of 0.1 m/s2. Joe’s
workout set of weights has a
mass of 200 kg. What is the
weight of the set on Planet X?
Ans. 20 N
The next four slides deal with
the same initial information.
What is the initial vertical velocity of
the object?
30 m/s
50
Ans. 23 m/s
What is the time in the air from
launch to landing at same height?
30 m/s
50
Ans. 4.6 s
What is the maximum height
reached by the object?
30 m/s
50
Ans. 26.5 m
What is the range for this
projectile?
30 m/s
50
Ans. 88.8 m
The following two slides are
based on the same initial
information.
What is time in air?
15 m/s
y
x
2m
Dx
Ans. 0.63 s
What is Dx?
15 m/s
y
x
2m
Dx
Ans. 9.5 m
The following three slides have
the same initial information.
How long will it take boat to cross
river?
6 km
12 km/h
B
4 km/h
Ans. ½ h
How far downstream will the boat
drift?
6 km
12 km/h
B
4 km/h
Ans. 2 km
What is the velocity of the boat
relative to the shore?
6 km
12 km/h
B
4 km/h
Ans. 12.6 km/h @
18.4 SE