The velocity-time graph of an object of mass m = 120 50 g is shown in figure. Observe the graph carefully and answer the following questions. (a) Calculate the force on the object in time interval 0 to 3 s. (b) Calculate the force on the object in the time interval 6 to 10 s. (c) Is there any time interval in which no force acts on the object? Justify your answer.

(a) Acceleration during interval 0 to 3s

𝑎₁ = ${𝑣−𝑢 \over 𝑡}$  = ${120−0\over3}$ = 40𝑚/s ²

Given mass, m = 50 g  = ${50\over1000}$ kg

∴ Force, 𝐹₁ = ma₁ = $({50\over1000})$ ×40  2N

(b) Acceleration during interval 6 to 10 s

𝑎₂ = ${𝑉_2−𝑉_1 \over 𝑡}$  = ${0 − 120\over ( 10−6)}$

= – ${120\over4}$ = – 30 m/s ²

Force, 𝐹₂ = ma₂ = $50\over1000$ × (-30) = – 1.5 N

(c) During time interval 3 to 6 s, the velocity of object is constant, so in this time interval, acceleration is zero and hence force, F (= ma) is zero.]