#### • Class 11 Physics Demo

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#### • accelerated uniform rectilinear motion

Question:Please give me the definition of the uniformly accelerated linear motion. Thanks.

Answers:Motion implies momentum, which implies velocity. Linear implies a straight line. Accelerating implies changing velocity. And uniform implies constancy. So, when a body moves in a straight line and accelerates at a constant rate, the body is said to have an uniformly accelerated linear motion.

Question:A cyclist is supposed to be at a destination at a definite time. If he travels at a rate of 15km/hr he will be and hour early. If he travels at a speed of 10km/hr he will be an hour late. At what speed should he travel to be on time? I think you have to use Distance= rate* time

Answers:Let the distance be x Speed = 15kmph Time = x/15 hours Let the time he has to reach be y hours x/15 = y - 1 y = x/15 + 1 (A) x/ 10 = y + 1 y = x/10 - 1 (B) (A) = (B) x/15 + 1 = x/10 -1 x/10 - x/15 = 2 MULTIPLY BY 30 3x - 2x = 60 x = 60 km 60/15 = 4 hours 60/5 = 12 km per hour ANSWER CHECK 60/15 = 4 hours 60/10 = 6 hours 60/12 = 5 hours

Question:1. batman is sitting in the batmobile at a spotlight. As the light turns green, Robin passes Batman in his lime green pinto at a constant speed of 60km/h. If batman gives chase, accelerating at constant rate of 10km/h/s, determine am completely off on my answers a. how long it takes batman to attain same speed? answer :6.0 b. how far Batman travels in this time? ans: 50m c. how long it takes for Batman to catch up to robin? ans : 12.0s 2. A squash ball makes contact with a squash racquet and changes from 15m/s to 25m/s east in 0.10s. determine the vector acceleration of the squash ball

Answers:a. The units as given are OK for this one. The speed changes by 10 km/h each second, and he wants to get to 60 km/h. So 60/10 = 6 seconds. b. You can use d = (1/2)at^2 for this, but to get an answer in meters you're going to have to convert the acceleration to m/sec^2. To do that, convert the km to meters (multiply by 1000) and the hr to seconds (divide by 3600). c. You can use d = (1/2)at^2 again, and again you need the value of a in m/sec^2. This time t is unknown. It is going to be more than 6 seconds and Batman is going to continue to accelerate (he won't catch Robin if he stops accelerating when he gets to 60, because Robin is far ahead of him, also doing 60). In the same time, Robin goes d = v*t, but you're going to have to convert his speed to m/sec also. Batman catches Robin when these distances are the same. (1/2)at^2 = v*t You can divide out one factor of t (1/2)at = v and you can rearrange that to solve for v. Actually come to think of it, you can use the original units of km/hr for v and km/hr/sec for a, since they are compatible in this equation. You've got km/hr on both sides so that would be OK. Number 2, just use the definition of acceleration. You have the change in velocity. You have the time. a = (change in velocity)/time

Question:Q 1.a body moving with constant speed has uniform motion while a freely falling object has non uniform motion. why? Q 2.can a body have acceleration while at rest? give eg. Q 3. what type of motion is associated with a pendulum? Q 4. what does the rate of change of angular velocity refer to? Q 5. a boy after going around a circular track of radius 'r' comes back to the starting point. a)what is the displacement of the body? b)what is the total distance covered by him?

Answers:Q1. Uniform motion definition (my guess): Same distance covered every second, which also means a constant velocity. Free fall has an increasing velocity every second. Q2. Yes. You are accelerating right now while reading this. Gravity is causing you to ALWAYS accelerate while on earth. Q3. Simple harmonic motion Q4. Angular acceleration Q5. The displacement is 0 (starting position minus ending position).The distance covered is 2*pi*r (circumference)