A scooter starting from rest moves with a constant acceleration for a time ∆t1, then with a constant velocity
A scooter starting from rest moves with a constant acceleration for a time ∆t1, then with a constant velocity for the next ∆t2, and finally with a constant deceleration for the next ∆t3, to come to rest. A 500 N man sitting on the scooter behind the driver manages to stay at rest with respect to the scooter without touching any other part. The force exerted by the seat on the man is
(a) 500 N throughout the journey
(b) less than 500 N throughout the journey
(c) more than 500 N throughout the journey
(d) > 500 N for time ∆t1, and ∆t3 and 500 N for ∆t2,.
1 Answers
(d) > 500N for time Δt1 and Δt3 and 500N for Δt2.
Explanation:
During the constant velocity for time Δt2 there is no relative movement between the man and the seat and only force applied by the seat on the man is Normal Force which is equal to weight of the man =500 N.
But during the acceleration (Δt1) and deceleration (Δt3) the seat exerts an addition force of friction on man in horizontal direction. Let this be F.
Now the force by seat on man is resultant of 500 N and F,
=√{(500)²+F²} N, which is >500 N.