Newton’s Second Law corrected the old belief that force is needed to maintain motion. This idea came from the philosopher ______.
Advertisements
Advertisements
प्रश्न
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 ______.
विकल्प
frictional force along westward.
muscle force along southward.
frictional force along south-west.
muscle force along south-west.
MCQ
रिक्त स्थान भरें
Advertisements
उत्तर
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 frictional force along south-west.
Explanation:
According to Newton’s second law of motion, only external forces can change the linear momentum of the system. The internal forces cannot change the linear momentum of system under consideration. If we take hockey players as a system, the external force which can change the direction of motion of the player is the force that must be friction between the ground and the shoes of player. The muscle force is the internal force, this cannot change the linear momentum of the player.
According to Newton’s Second Law, The rate of change of linear momentum of a body is equal to the external force applied on the body or F = dp/dt. So, the external force must be in the direction of change in momentum.
As shown in the diagram,
Let OA = p1
= Initial momentum of player northward
AB = p2
= Final momentum of the player towards west
Clearly OB = OA + AB
According to the problem, mass = 2 kg
The position of the particle is given here as a function of time, x(t) = pt + qt2 + rt3 By differentiating this equation w.r.t. time we get velocity of the particle as a function of time.
v = dx/dt = p + 2 qt + 3 rt2
If we again differentiate this equation w.r.t. time, we will get an acceleration of the particle as a function of time.
a = dv/dt = 0 + 2q + 6rt
At t = 2 s; a = 2q + 6 × 2 × r
= 2 q + 12 r
= 2 × 4 + 12 × 5
= 8 + 60
= 68 m/s
Force = F = ma
= 2 × 68
= 136 N
Change in momentum = p2 – p1
= AB – OA
= AB + (– OA)
= Clearly the change in momentum is OR will be along southwest, so the direction of force will also be along southwest.
shaalaa.com
क्या इस प्रश्न या उत्तर में कोई त्रुटि है?
APPEARS IN
संबंधित प्रश्न
A constant retarding force of 50 N is applied to a body of mass 20 kg moving initially with a speed of 15 ms–1. How long does the body take to stop?
A body of mass 0.40 kg moving initially with a constant speed of 10 m s–1 to the north is subject to a constant force of 8.0 N directed towards the south for 30 s. Take the instant the force is applied to be t = 0, the position of the body at that time to be x = 0, and predict its position at t = –5 s, 25 s, 100 s.
The rear side of a truck is open and a box of 40 kg mass is placed 5 m away from the open end as shown in Figure. The coefficient of friction between the box and the surface below it is 0.15. On a straight road, the truck starts from rest and accelerates with 2 m s–2. At what distance from the starting point does the box fall off the truck? (Ignore the size of the box).
Two objects A and B are thrown upward simultaneously with the same speed. The mass of A is greater than that of B. Suppose the air exerts a constant and equal force of resistance on the two bodies.
Two blocks of equal mass m are tied to each other through a light string. One of the blocks is pulled along the line joining them with a constant force F. Find the tension in the string joining the blocks.
Two blocks A and B of mass mA and mB , respectively, are kept in contact on a frictionless table. The experimenter pushes block A from behind, so that the blocks accelerate. If block A exerts force F on block B, what is the force exerted by the experimenter on block A?
Suppose the ceiling in the previous problem is that of an elevator which is going up with an acceleration of 2.0 m/s2. Find the elongation.
Show that the rate of change of momentum = mass × acceleration. Under what condition does this relation hold?
State the Newton's second law of motion. What information do you get from it?
Use Newton's second law of motion to explain the following instance :
A cricketer pulls his hands back while catching a fast moving cricket ball .
State two factors which determine the momentum of a body.
Name the physical entity used for quantifying the motion of a body.
Name the physical quantity which equals the rate of change of linear momentum.
Use Newton's second law to explain the following:
While catching a fast moving ball, we always pull our hands backwards.
A stone is dropped from a cliff 98 m high.
How long will it take to fall to the foot of the cliff?
A stone is thrown vertically upward with a velocity of 9.8 m/s. When will it reach the ground?
The motion of a particle of mass m is given by x = 0 for t < 0 s, x(t) = A sin 4 pt for 0 < t < (1/4) s (A > o), and x = 0 for t > (1/4) s. Which of the following statements is true?
- The force at t = (1/8) s on the particle is – 16π2 Am.
- The particle is acted upon by on impulse of magnitude 4π2 A m at t = 0 s and t = (1/4) s.
- The particle is not acted upon by any force.
- The particle is not acted upon by a constant force.
- There is no impulse acting on the particle.
