Question

A person walks 750m due north, then 250m due east. If the entire walk

takes 13 minutes, find the person's average velocity?

An object moves along a straight line. First it travels at a velocity of

12m/s for 6s and then continues at the same direction with 20m/s for 3s.

What is its average speed?

For 10s, the velocity of a car which travels with a constant acceleration,

changes from 10m/s to 20m/s. How far does the car travel?

A cyclist covers a distance of 15 miles in 2 hours. Calculate his speed.

A boy walks at a speed of 4 kmph. How much time does he take to walk a

distance of 20 km?

A car takes 4 hours to cover a distance, if it travels at a speed of 40 mph. What should be its speed to cover the same distance in 1.5 hours?

If a person drives his car in the speed 50 miles per hour, how far can he

cover in 90 minutes?

Answer 1

a.

$$v_{ave}=\dfrac{750m+250m}{13min}=\dfrac{1000}{13}m/min$$

b.

$$v_{ave}=\dfrac{12m/s(6s)+20m/s(3s)}{6s+3s}=\dfrac{44}{3}m/s$$

c.

$$v_1=v_0+at_1=>a=\dfrac{v_1-v_0}{t_1}$$

$$s_1=v_0t_1+\dfrac{at_1^2}{2}$$

$$s_1=v_0t_1+\dfrac{(v_1-v_0)t_1}{2}$$

$$s_1=\dfrac{(v_1+v_0)t_1}{2}$$

$$s_1=\dfrac{(20m/s+10m/s)10s}{2}=150m$$

d.

$$v=15mi/2h=7.5\ mi/h$$

e.

$$t=\dfrac{20km}{4km/h}=5hours$$

f.

$$v=\dfrac{40mi/h(4h)}{1.5h}=\dfrac{320}{3}mi/h$$

$\dfrac{320}{3}$ mph

g. $90min=1.5h$

$$50mi/h(1.5h)=75mi$$

75 miles