Patterns Across Space and Time Motion Worksheet ... - Archives

3. A car travels 120 km along a road at 40 km/hr and then immediately returns along the same
road at a speed of 60 km/hr.
(a) How long does each leg of the trip take?
v = d/t so t = d/v. Thus t = 120/40 = 3 hours for the outward trip and t = 120/60 = 2
hours for the return trip.
(b) What is the average speed for the round trip? The average speed is total distance over
total time which is 240/5=48 km/hr. Notice the average speed is not 50 km/hr since the
car spends more time going at the slower speed of 40 km/hr.
(c) What is the average velocity for the round trip? Since the car returns to the starting
point the average velocity is zero.
4. In each of the following cases state whether the motion is accelerated or not.
(a) A meteoroid traveling in outer space with negligible gravitational influence.
No acceleration
(b) A satellite orbiting earth at a constant speed of 30,000 km/hr
Acceleration. The speed is constant but the direction changes.
(c) An ice skater coasting on ice in a straight line.
No acceleration assuming friction is negligible
(d) A skydiver falling at terminal velocity?
No acceleration - the skydiver is no longer gaining speed
5. A car is moving at a constant speed of 30 km/hr. The driver then presses harder on the
accelerator causing an acceleration of 2.25 km/hr/sec, which she maintains for 4 seconds.
How fast is the car moving at the end of 4 seconds?
in 4 seconds the car gains 4×2.25 = 9 km/hr so the car is moving at 39 km/hr after 4 seconds.