Homework 2 - Equations Of Motion
1. A labourer on scaffolding outside one of the physics classrooms drops
a wrench. A student times it as it falls past the 2m tall classroom window and
found that it took 0.6s to fall . Calculate the wrench’s initial velocity as it
appears at the top of the window.
2. A train decelerates from 12.0 ms-1 to 5.0 ms-1 while travelling a distance of
119.0 m along a straight track. Calculate the deceleration of the train.
3. A skier sets off from rest and accelerates uniformly down a straight ski run.
After 4·50 seconds she reaches a speed of 23·0 m s-1. After this time the skier no
longer accelerates but continues to travel at 23·0 m s-1 for a further 11·0 s.
Calculate:
a) the acceleration of the skier during the first 4·50 s of her run.
b) the total distance travelled by the skier.
4. In a staggered sprint race, sprinters P and Q both start the race at the same time
but from different starting positions on the track.
The stagger is such that both sprinters reach XY, as shown below, at the same
time.
Sprinter P has a constant acceleration of 1.6 ms-2 from the start line to the line
XY. Sprinter Q has a constant acceleration of 1.2 ms-2 from the start line to XY.
a) Calculate the time taken by the sprinters to reach line XY.
b) Find the speed of each sprinter at this line.
c) What is the distance, in metres, between the starting lines for
sprinters P and Q?
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Numerical Answers
Exercise 2
1. 0.393 m s -1
2. 0.5 m s-2
3. (a) 5.11 m s-2
(b) 305 m
4. (a) 5 s
(b) P: 8 m s-1, Q: 6 m s-1
(c) 5 m
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