Class 11 Physics · 42 questions · 0 with answers
A ball is travelling with uniform translatory motion. This means that
A metre scale is moving with uniform velocity. This implies
A cricket ball of mass 150 g has an initial velocity u = (3ˆi + 4 ˆj) m s −1 and a final velocity v = − (3ˆi + 4 ˆj) m s −1 after being hit. The change in momentum (final momentum-initial momentum) is (in kg m s1)
In the previous problem (5.3), the magnitude of the momentum transferred during the hit is
Conservation of momentum in a collision between particles can be understood from
A hockey player is moving northward and suddenly turns westward with the same speed to avoid an opponent. The force that acts on the player is
A body of mass 2kg travels according to the law x (t ) = pt + qt 2 + rt 3 where p = 3 m s−1 , q = 4 m s−2 and r = 5 m s−3 . The force acting on the body at t = 2 seconds is
A body with mass 5 kg is acted upon by a force F = ( –3ˆi + 4 ˆj ) N. If its initial velocity at t = 0 is v = ( 6ˆi -12 ˆj ) m s –1 , the time at which it will just have a velocity along the y-axis is
A car of mass m starts from rest and acquires a velocity along east v = v ˆi ( v > 0 ) in two seconds. Assuming the car moves with uniform acceleration, the force exerted on the car is
The motion of a particle of mass m is given by x = 0 for t < 0 s, x( t ) = A sin4p t for 0 < t <(1/4) s (A > o), and x = 0 for t >(1/4) s. Which of the following statements is true?
In Fig. 5.1, the co-efficient of friction between the floor and the body B is 0.1. The co-efficient of friction between the bodies B and A is 0.2. A force F is applied as shown on B. The mass of A is m/2 and of B is m. Which of the following statements are true?
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Mass m1 moves on a slope making an angle θ with the horizontal and is attached to mass m2 by a string passing over a frictionless pulley as shown in Fig. 5.2. The co-efficient of friction between m1 and the sloping surface is µ. Which of the following statements are true? m1 m2
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In Fig. 5.3, a body A of mass m slides on plane inclined at angle θ1 to the horizontal and µ1 is the coefficent of friction between A and the plane. A is connected by a light string passing over a frictionless pulley to another body B, also of mass m, sliding on a frictionless plane inclined at angle θ2 to the horizontal. Which of the following statements are true?
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Two billiard balls A and B, each of mass 50g and moving in opposite directions with speed of 5m s –1 each, collide and rebound with the same speed. If the collision lasts for 10–3 s, which of the following statements are true?
A body of mass 10kg is acted upon by two perpendicular forces, 6N and 8N. The resultant acceleration of the body is
A girl riding a bicycle along a straight road with a speed of 5 m s–1 throws a stone of mass 0.5 kg which has a speed of 15 m s–1 with respect to the ground along her direction of motion. The mass of the girl and bicycle is 50 kg. Does the speed of the bicycle change after the stone is thrown? What is the change in speed, if so?
A person of mass 50 kg stands on a weighing scale on a lift. If the lift is descending with a downward acceleration of 9 m s–2, what would be the reading of the weighing scale? (g = 10 m s–2 )
The position time graph of a body of mass 2 kg is as given in Fig. 5.4. What is the impulse on the body at t = 0 s and t = 4 s. Fig. 5.4
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A person driving a car suddenly applies the brakes on seeing a child on the road ahead. If he is not wearing seat belt, he falls forward and hits his head against the steering wheel. Why?
The velocity of a body of mass 2 kg as a function of t is given by v(t ) = 2t ˆi + t 2 ˆj . Find the momentum and the force acting on it, at time t= 2s.
A block placed on a rough horizontal surface is pulled by a horizontal force F. Let f be the force applied by the rough surface on the block. Plot a graph of f versus F.
Why are porcelain objects wrapped in paper or straw before packing for transportation?
Why does a child feel more pain when she falls down on a hard cement floor, than when she falls on the soft muddy ground in the garden?
A woman throws an object of mass 500 g with a speed of 25 m s1.
Why are mountain roads generally made winding upwards rather than going straight up?
A mass of 2kg is suspended with thread AB (Fig. 5.5). Thread CD of the same type is attached to the other end of 2 kg mass. Lower thread is pulled gradually, harder and harder in the downward directon so as to Fig. 5.5 apply force on AB. Which of the threads will break and why?
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In the above given problem if the lower thread is pulled with a jerk, what happens?
Two masses of 5 kg and 3 kg are suspended with help of massless inextensible strings as shown in Fig. 5.6. Calculate T 1 and T 2 when whole system is going upwards with acceleration = 2 m s 2 (use g = 9.8 m s –2). Fig. 5.6 Laws of Motion
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Block A of weight 100 N rests on a frictionless inclined plane of slope angle 30° (Fig. 5.7). A flexible cord attached NA F to A passes over a frictonless pulley and is connected to w block B of weight W. Find the weight W for which the 30° 30° system is in equilibrium. mg mg cos 30°
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A block of mass M is held against a rough vertical wall by pressing it with a finger. If the coefficient of friction between mg the block and the wall is µ and the acceleration due to Fig. 5.7 gravity is g, calculate the minimum force required to be applied by the finger to hold the block against the wall ?
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A 100 kg gun fires a ball of 1kg horizontally from a cliff of height 500m. It falls on the ground at a distance of 400m from the bottom of the cliff. Find the recoil velocity of the gun. (acceleration due to gravity = 10 m s–2)
Figure 5.8 shows (x, t), (y, t ) diagram of a particle moving in 2-dimensions. 1s 2s 3s t
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A person in an elevator accelerating upwards with an acceleration of 2 m s–2, tosses a coin vertically upwards with a speed of 20 m s1. After how much time will the coin fall back into his hand? ( g = 10 m s–2)
There are three forces F1, F2 and F3 acting on a body, all acting on a point P on the body. The body is found to move with uniform speed.
When a body slides down from rest along a smooth inclined plane making an angle of 45° with the horizontal, it takes time T. When the same body slides down from rest along a rough inclined plane making the same angle and through the same distance, it is seen to take time pT, where p is some number greater than 1. Calculate the co-efficient of friction between the body and the rough plane.
Figure 5.9 shows (v x ,t ),and(vy ,t ) diagrams for a body of unit mass. Find the force as a function of time. vx vy (m s–1) (m s–1) 1 1 1s 2s t O 1s 2s 3s t
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A racing car travels on a track (without banking) ABCDEFA (Fig. 5.10). ABC is a circular arc of radius 2 R. CD and FA are straight paths of length R and DEF is a circular arc of radius R = 100 m. The co-effecient of friction on the road is µ = 0.1. The maximum speed of the car is 50 m s–1. Find the minimum time for completing one round. 90° R D O 2R Fig. 5.10
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The displacement vector of a particle of mass m is given by r(t ) = ˆi A cos ω t + ˆj B sin ω t .
A cricket bowler releases the ball in two different ways
There are four forces acting at a point P produced by strings as shown in Fig. 5.11, which is at rest. Find the forces F1 and F2 . 2N 1N 45° 45° 45° F1 90° F2 Fig. 5.11
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A rectangular box lies on a rough inclined surface. The co-efficient of friction between the surface and the box is µ. Let the mass of the box be m.
A helicopter of mass 2000kg rises with a vertical acceleration of 15 m s–2. The total mass of the crew and passengers is 500 kg. Give the magnitude and direction of the (g = 10 m s–2)