Download Newton`s 1 Law of Motion - Answers

Newton's 1st Law of Motion - Answers
1. Who’s work did Newton base his 1st law of motion on?
2. When did Newton publish his laws?
Galileo
1687
3. What is the basic difference between Aristotle’s view of motion and Galileo’s?
Aristotle said that the natural state of objects is to be at rest while Galileo said that their
natural state is to have a constant velocity (including a velocity of zero).
4. What is needed to change the speed of an object? An unbalanced force
5. What is needed to change the direction an object is travelling? An unbalanced force
6. What is needed to change the velocity of an object? An unbalanced force
7. What will happen to an object that is experiencing balanced forces?
It will have a constant velocity (travel straight at a constant speed)
8. Use the 1st Law to decide if the forces acting on the objects are balanced or unbalanced in
each of the following cases. Also state whether the net force is zero, or not zero.

Balanced or
F  0
unbalanced?
or 0 ?
a parachutist is falling straight down at constant speed
B
=0
a ball is dropped and is accelerating straight down
U
0
a car slides straight off an icy curve without slowing down
B
=0
a car successfully travels around a curve in the road
U
0
a train pulls away from station, starting from rest
U
0
a box is pushed straight at a constant speed on rough surface
B
=0
a box slides to a stop while traveling straight on a rough surface
U
0
the moon orbits around the Earth in an almost circular path at a
constant speed
U
0
a bubble rises straight up through water without speeding up
B
=0
a skier skies down a straight hill without speeding up or slowing
B
=0
a feather falls through the air on a twisting path at a constant
speed
U
0
a hot air balloon rises at 45° above the horizontal along a straight
line at a constant speed
B
=0
Section 2.2: Questions # 1, 2 (p. 76)
1. The snowboard will slow down since it experiences a backwards force form the rough patch
of snow. The person on the snow board might continue forward at their original speed if there
is not enough friction between their feet and the board to slow them down too. This would
result in them moving forward relative to the board (appearing to fall forward).
2. No, the ball won’t hit you in the face because it will still be moving forward with the same
velocity as you (50 km/h) since there is no unbalanced force forwards or backwards acting on
the ball. It will have no horizontal velocity relative to you so it can’t move horizontally towards
your face.
SPH4U Dynamics
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