Newton’s Second Law corrected the old belief that force is needed to maintain motion. This idea came from the philosopher:
Advertisements
Advertisements
Question
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 ______.
Options
frictional force along westward.
muscle force along southward.
frictional force along south-west.
muscle force along south-west.
MCQ
Fill in the Blanks
Advertisements
Solution
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
Is there an error in this question or solution?
APPEARS IN
RELATED QUESTIONS
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.
A batsman deflects a ball by an angle of 45° without changing its initial speed which is equal to 54 km/h. What is the impulse imparted to the ball? (Mass of the ball is 0.15 kg.)
Suppose you are running fast in a field and suddenly find a snake in front of you. You stop quickly. Which force is responsible for your deceleration?
A person says that he measured the acceleration of a particle to be non-zero even though no force was acting on the particle.
Find the reading of the spring balance shown in the following figure. The elevator is going up with an acceleration g/10, the pulley and the string are light and the pulley is smooth.
In the following figure, m1 = 5 kg, m2 = 2 kg and F = 1 N. Find the acceleration of either block. Describe the motion of m1 if the string breaks but F continues to act.
In the previous problem, suppose m2 = 2.0 kg and m3 = 3.0 kg. What should be the mass m, so that it remains at rest?
Find the acceleration of the 500 g block in the following figure.
A monkey of mass 15 kg is climbing a rope fixed to a ceiling. If it wishes to go up with an acceleration of 1 m/s2, how much force should it apply on the rope? If the rope is 5 m long and the monkey starts from rest, how much time will it take to reach the ceiling?
An aeroplane is moving uniformly at a constant height under the action of two forces (i) Upward force (lift) and (ii) Downward force (weight). What is the net force on the aeroplane?
A force of 10 N acts on a body of mass 2 kg for 3 s, initially at rest. Calculate : The velocity acquired by the body
A stone is dropped freely from the top of a tower and it reaches the ground in 4 s. Taking g = 10m s-2, calculate the height of the tower.
Calculate the velocity of a body of mass 0.5 kg, when it has a linear momentum of 5 Ns.
A body of mass 200 g is moving with a velocity of 5 ms−1. If the velocity of the body changes to 17 ms−1, calculate the change in linear momentum of the body.
State two factors which determine the momentum of a body.
Use Newton's second law to explain the following:
We always prefer to land on sand instead of hard floor while taking a high jump.
A metre scale is moving with uniform velocity. This implies ______.
