# CBSE Class 11-science Physics Motion in Two Dimensions

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- what is RPM.is it a unit of frequency or angular velocity. If a particle complete 1 revolution in 1 sec find both sec
- The position of a particle at any instant is given by .
At what instant the velocity vector will make an angle 45
^{o}with X-axis. - A particle starts from the origin at t = 0 with a velocity of m/s and moves in XY plane with a constant acceleration of . (a) At what time is the X-coordinate of the particle 16 m? (b) What is the Y-coordinate of the particle at that time?
- A cyclist starts from the center O of circle of park of radius 1 km, reaches the edge P of the park, then cycles along the circumference to point Q and returns to the centre along QO as shown. If the round trip takes 10 minutes, then what is (a) net displacement (b) average velocity (c) average speed of the cyclist?
- The position vector of particle at any instant is given by . Show that velocity and acceleration of particle at any instant are perpendicular to each other.
- An aircraft is flying at a height of 3400m above the ground. If the angle subtended at a ground observation point by the aircraft positions 10 s apart in 30
^{o}, what is the speed of the aircraft? - A passenger arriving in a new town wishes to go from the station to a hotel located 10 km away on a straight road from the station. A dishonest taxidriver takes him along a circuitous path 23 km long and reaches the hotel in 28 minute. What is: (a) the average speed of taxi (b) the magnitude of average velocity. Are the two equal?
- Two particles A and B start from P and move along a circular path in anticlockwise and clockwise direction respectively. They complete one fourth of the journey in the same time. Do they have same average velocities?
- A man can swim with speed of 4 km/hr in still water. How long does he take to cross the river 1 km wide if the river flows steadily at 3 km/hr and he makes his stroke normal to the river current? How far down the river does he go when he reaches the other bank?
- A river 100m wide is running downwards at the rate of 1 km per hour and a swimmer who can swim at the rate of 3.6 km/hr wishes to reach a point just opposite. Along which direction should he strike and how long will he take to cross the river?

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