One car moving on a straight road covers one third of distance with 20 ,km/hr and rest with 60, km/h

English

Gujarati

Hindi

2.Motion in Straight Line

medium

One car moving on a straight road covers one third of the distance with $20 \,km/hr $ and the rest with $60\, km/hr$. The average speed is..........$km/hr$

A

$40$

B

$80$

C

$46\frac{2}{3}$

D

$36$

Solution

(d)Average speed $ = \frac{{{\rm{Total\, distance }}}}{{{\rm{Total\, time}}}}$$ = \frac{x}{{{t_1} + {t_2}}}$

$ = \frac{x}{{\frac{{x/3}}{{{v_1}}} + \frac{{2x/3}}{{{v_2}}}}}$$ = \frac{1}{{\frac{1}{{3 \times 20}} + \frac{2}{{3 \times 60}}}} = 36\;km/hr$

Standard 11

Physics

Share

Similar Questions

A cyclist starts from the centre $O$ of a circular park of radius one kilometre, reaches the edge $P$ of the partk. Then cycles along the circumference and returns to the centre along $QO$ as shown in the figure. If the round trip takes ten minutes, the net displacement and average speed of the cyclist (in metre and kilometre per hour respectively) is

medium

A $100\, m$ long train is moving with a uniform velocity of $45\, km/hr$. The time taken by the train to cross a bridge of length $1 \,km$ is………$s$

medium

A car moves from $X$ to $Y$ with a uniform speed $v_1$ and returns to $Y$ with a uniform speed $v_2$ . The average speed for this round trip is

medium

(AIPMT-2007)

A particle is constrained to move on a straight line path. It returns to the starting point after $10\, sec$. The total distance covered by the particle during this time is $30\, m$. Which of the following statements about the motion of the particle is false

easy

A person goes from point $P$ to point $Q$ covering $1 / 3$ of the distance with speed $10 \,km / h$, the next $1 / 3$ of the distance at $20 \,km / h$ and the last $1 / 3$ of the distance at $60 \,km / h$. The average speed of the person is ………… $km / h$

medium

(KVPY-2017)